View Full Version : The Iran-Iraq War 1980-1988: books plus

06-04-2008, 12:38 AM
I'm compiling a list of reads for an upcoming deployment, and am looking for a recommended book that covers the Iran-Iraq War 1980-1988. I'm particularly interested in the operational/tactical moves made during the ebb and flow of the front lines, and less concerned about the peripheral issues of the Tanker War that ensued.

Any suggestions out there?

06-04-2008, 02:19 AM
Lessons Learned: The Iran-Iraq War (http://www.amazon.com/Lessons-Learned-Iran-Iraq-War/dp/9992733799) by Stephen Pelletiere and Douglas Johnson, originally published by SSI in '91. An earlier draft version, published by the USMC as FMFRP 3-203, is available online at FAS (http://www.fas.org/man/dod-101/ops/war/docs/3203/).

A decent companion volume is Ronald Bergquist's The Role of Airpower in the Iran-Iraq War (http://aupress.au.af.mil/Books/Bergquist/Bergquist_B25.pdf) published right at the end of the war in '88. The link is to a pdf version, or you can get a hard copy through Amazon (http://www.amazon.com/Role-Airpower-Iran-Iraq-War/dp/0898759757).

If you really want exhaustive detail, then try Cordesman and Wagner's 647 page The Lessons Of Modern War Volume II: The Iran-Iraq War (http://www.amazon.com/Lessons-Modern-War-Iran-iraq-Vol/dp/0813309557)

06-04-2008, 02:33 AM
I cannot personally vouch for these, but these titles are in the endnotes to Chapter 7 of Pollack's "The Persian Puzzle."

The Lessons of Modern War, vol. 2, The Iran-Iraq War (http://www.amazon.com/Lessons-Modern-War-Iran-iraq-Vol/dp/0813309557/ref=sr_1_1?ie=UTF8&s=books&qid=1212546675&sr=8-1) (Cordesman and Wagner)
The Longest War: The Iran-Iraq Military Conflict (http://www.amazon.com/Longest-War-Iran-Iraq-Military-Conflict/dp/0415904072/ref=sr_1_2?ie=UTF8&s=books&qid=1212546737&sr=1-2)(Hiro)

Update: This from the endnotes to "Eternal Iran" by Rubin and Clawson...

The Cordesman/Wagner piece is identified as "the definitive study", but they point out an "excellent short summary by Karsh The Iran-Iraq War, 1980-1988 (http://www.amazon.com/Iran-Iraq-War-1980-1988-Essential-Histories/dp/1841763713/ref=sr_1_1?ie=UTF8&s=books&qid=1212547294&sr=1-1) and state the Hiro's book, above, "is inconsistent, mixing solid research and significant errors." Lastly they state that "Iraqi military performance during the war - though not the war as a whole - is analyzed in Kennth Pollack, Arabs at War: Military Effectiveness, 1948-1991 (http://www.amazon.com/Arabs-War-Military-Effectiveness-1948-1991/dp/0803287836/ref=sr_1_1?ie=UTF8&s=books&qid=1212547243&sr=1-1)."

06-04-2008, 02:58 AM
Offhand, FMFRP 3-203 Lessons Learned: The Iran-Iraq War, Volume I, USMC, 1990 (http://www.theblackvault.com/documents/wwii/marine1/3203.pdf) (sorry, just noticed that Jedburgh posted it too,) is more or less along the lines of what you may be looking for. I have, or at least used to have, some other docs on the subject, but I'll have to dig to find them, if I even still have them. There's also NTC Handbook 91-100 The Iraqi Army: Organization and Tactics (http://council.smallwarsjournal.com/FMFRP 3-203 Lessons Learned: The Iran-Iraq War, Volume I, USMC, 1990), but it completely skips actual battles, and simply deals with doctrine and TO&E's. There's also this CGSC Thesis which is rather interesting, Tactical Evolution in the Iraqi Army: The Abadan Island and Fish Lake Campaigns of the Iran-Iraq War (http://cgsc.cdmhost.com/cdm4/item_viewer.php?CISOROOT=/p4013coll2&CISOPTR=1380).

Also try:

The Iraqi Way of War: An Operational Assessment (http://cgsc.cdmhost.com/cdm4/item_viewer.php?CISOROOT=/p4013coll3&CISOPTR=1675)

Saddam Hussein's First War: An Assessment of Iraqi Operational Art in the Iran-IraqWar (http://cgsc.cdmhost.com/cdm4/item_viewer.php?CISOROOT=/p4013coll3&CISOPTR=838)

Operational Art: The Missing Link in the Iran-Iraq War (http://cgsc.cdmhost.com/cdm4/item_viewer.php?CISOROOT=/p4013coll3&CISOPTR=2014)

I think there was a CNA paper several years ago about some of this stuff.
This is also useful, even if it is from the other side:

The Evolution of Iranian Warfighting during the Iran-Iraq War: When Dismounted Light Infantry Made the Difference (http://stinet.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA473957) (originally published in Infantry Magazine)

Try and see if you can get a hold of DDB-2600-61 23-90, Iraqi Ground and Air Force Doctrine, Tactics, and Operations, DIA, 1990.

06-04-2008, 10:50 AM
Lessons Learned: The Iran-Iraq War (http://www.amazon.com/Lessons-Learned-Iran-Iraq-War/dp/9992733799) by Stephen Pelletiere and Douglas Johnson, originally published by SSI in '91. An earlier draft version, published by the USMC as FMFRP 3-203, is available online at FAS (http://www.fas.org/man/dod-101/ops/war/docs/3203/).

A decent companion volume is Ronald Bergquist's The Role of Airpower in the Iran-Iraq War (http://aupress.au.af.mil/Books/Bergquist/Bergquist_B25.pdf) published right at the end of the war in '88. The link is to a pdf version, or you can get a hard copy through Amazon (http://www.amazon.com/Role-Airpower-Iran-Iraq-War/dp/0898759757).

If you really want exhaustive detail, then try Cordesman and Wagner's 647 page The Lessons Of Modern War Volume II: The Iran-Iraq War (http://www.amazon.com/Lessons-Modern-War-Iran-iraq-Vol/dp/0813309557)

If you're interested in the Johnson--Pelletiere monograph, don't buy it from Amazon! It makes us nuts that used book dealers take free publications and sell them. If you want it, I'll see if I can find one laying around SSI. If not, I'll loan you mine.

06-04-2008, 12:37 PM
Splendid references gentlemen. I actually prefer smaller articles that focus the topic, and will look to the Cordesman book (for the actual deploy) after I have digested these gems over the next few weeks.

06-15-2008, 11:31 PM
All were excellent recommendations. The articles dealing with the beginning of the war and one of the latter phases, as well as the Fish Lake material, was excellent and just what I was seeking. On to the Cordesman book.

SWJ Blog
04-10-2012, 11:04 AM
Egyptian Field Marshal Abdul-Halim Abu Ghazalah on the Combat Tactics and Strategy of the Iran-Iraq War (http://smallwarsjournal.com/jrnl/art/three-part-essay-highlighting-egyptian-field-marshal-abdul-halim-abu-ghazalah%E2%80%99s-1993-book-o)

SWJ Blog
12-07-2012, 11:02 AM
Saddam’s Generals: Perspectives of the Iran-Iraq War (http://smallwarsjournal.com/jrnl/art/saddam%E2%80%99s-generals-perspectives-of-the-iran-iraq-war)

02-01-2013, 03:20 PM
There is a newly published book 'The Iran-Iraq War: New International Perspectives' edited by Nigel Ashton and Bryan Gibson; pub. Routledge, 2012. It has no reviews on Amazon.com or the UK Amazon site, perhaps the US$115 helps to explain:http://www.amazon.com/Iran-Iraq-War-International-Perspectives-History/dp/0415685249/ref=sr_1_1?s=books&ie=UTF8&qid=1359730592&sr=1-1&keywords=The+Iran-Iraq+War%3A+New+International+Perspectives

SWJ Blog
07-13-2016, 03:21 PM
How the International Community’s “Blind-Eye” Towards the Iran-Iraq War Paved the Way for Violence and Conflict in the Region (http://smallwarsjournal.com/jrnl/art/how-the-international-community%E2%80%99s-%E2%80%9Cblind-eye%E2%80%9D-towards-the-iran-iraq-war-paved-the-way-for-v)

12-20-2016, 09:54 PM
Slightly late for Christmas, but nevertheless, Helion Publishing (UK) (http://www.helion.co.uk/catalogsearch/result/?q=africa%40war) released three new volumes from its 'Middle East@War' series in these days, as follows:

The Iran-Iraq War. Volume 1: The Battle For Khuzestan, September 1980-May 1982 (https://www.amazon.com/Iran-Iraq-War-Khuzestan-September-1980-May/dp/1911096567)

The Iran-Iraq War. Volume 2: Iran Strikes Back, June 1982-December 1986 (https://www.amazon.com/Iran-Iraq-War-Strikes-1982-December-Middle/dp/1911096575/ref=pd_bxgy_14_img_2?_encoding=UTF8&psc=1&refRID=4Y1RASPGZY8GVD530SSS)

Yes, sure, there are meanwhile about 20 or so histories of this war in English language (plus some three times as many in different other languages). So, what's making these two volumes 'special', why should one buy or at least read them?

Sure, as one of co-authors, I'm biased. But, this project is the first time ever that really excellent sources - including loads of official documentation - from all involved parties were available. We could not only count on help from a number of former Iraqi Army generals, or gentlemen involved in Project Harmony and similar, but also on a number of well-placed sources in Iran (although far more 'clandestine'). If nothing else, several gentlemen from the latter country helped through provision of write-ups summarizing operational history of major Army units, plus the IRGC, of course.

Ted Hooton went to immense extensions to extract new materials from official archives in the USA, the UK, and Israel, rounding up the story.

Result of all the help we've got during this project is unprecedentedly detailed info on planning and conduct of combat operations: these two 'thiny' books (DIN A4 format, but only 112 pages) are so stuffed full with info and details, so full of exclusive information, that they read like one of 'usual' books about some WWII campaigns (say, '...commander XY then turned his Brigade around and assaulted in direction...').

Content-wise, both volumes are organized in chronological fashion, i.e. chapters by major phases or offensives. Of course, Volume 1 has a lots of 'introduction', detailing pre-war build-ups on both sides.

Overall, I'm sure they are still going to contain plenty of 'news' even for readers with lots of knowledge about this conflict. From my POV, these are likely to become best books to this topic for a while longer (and yes, I wouldn't go for anything less, but even my first reaction upon seeing the first draft for manuscripts of Volumes 1 and 2 was that they are certainly far better than anything else I've ever seen anywhere else - or ever expected we could manage).

BTW, volumes 3 and 4 are already half-way through preparation, too.

Volume 1:
- Background to a Bloody War (geo-political backgrounds)
- Two Armies (military build-up in Iran and Iraq)
- From Border War to Invasion ('skirmishing' along the frontier in August and September)
- The Invasion of Khuzestan (first phase of Iraqi invasion)
- The Iranians Strike Back (Iranian counteroffensives of late 1980 and early 1981)
- The Writing on the Wall (Iranian counteroffensives of 1981)
- Disaster for Iraq (Iranian offensive in 1982)

Volume 2:
- An Unholy Bloodbath (campaigns of 1983)
- First Battle in the Marshes (Operation Khaiber, 1984)
- The Slough of Despond (Iranian offensive in 1985)
- The Thriving Armourers (re-supply efforts of both sides mid through the war)
- The Brilliant Blow (Faw Offensive of 1986)


The third volume is at least as 'special', although not covering a comparatively 'important' story: Hawker Hunters at War, Iraq And Jordan, 1958-1967 (https://www.amazon.com/Hawker-Hunters-At-War-1958-1967/dp/1911096257/ref=sr_1_8?s=books&ie=UTF8&qid=1482270058&sr=1-8)

This one came into being as an 'offshot' of the Arab MiGs book-series (a six-volume operational history of Arab air forces at war with Israel, 1955-1973), and in cooperation with Mrs Patricia Salti, leading historian of the Royal Jordanian Force.

The story is 'limited' to this specific period because this was so distinct in development of both the Iraqi and Jordanian air forces: both were dominated by Hunters, and indeed: one could say that the history of Iraq as a country was dominated by 'British-trained Hunter pilots' for much of the 1960s. Iraqis were the first to fly Hunters in combat: not during some war with Israel, but during one of about 20 coups that completely destabilised the country during that period.

In that sense, particularly interesting to research and reconstruct was the story of Capt Munthir al-Windawi, who played a crucial role during (at least) two of coups in question - and that while flying Hunters.

Nearly half of the book is related to reconstructing Iraqi and Jordanian ops against Israel during the June 1967 War. This resulted in lots of new details and conclusions - many of which are not necessarily 'in line' with stories published to this topic until now.


Chapter 1: Special Relationship
Backgrounds about Iraqi and Jordanian air force, their cooperation with the UK etc., spanning times from the 1920s until 1958.

Chapter 2: Crisis of 1958
This chapter describes repercussions of the Suez War of 1956 upon Iraq and Jordan, and then continues with description of Hunter-acquisition process by Iraq, followed by Jordan, i.e. spanning times 1956-1958.

Chapter 3: New Start in Iraq
Centrepiece is the story of successive coups in Iraq - all of which saw intensive involvement of IrAF Hunters - and Iraq's repeated orders for Hunters, from 1963-1965 period.

Chapter 4: First Battles with Mirages
Similar chapter covering operational history of Hunters in Jordan of the early 1960s; that is, training, training, training, some maintenance problems, and then more training, followed by first clash with Israelis, in December 1964. It is concluding with the Air Battle of Samu, on 13 November 1966, in the course of which co-author Salti lost her husband.

Chapter 5: June 1967 War
In essence, 'IrAF and RJAF at war with Israel, June 1967'.

Chapter 6: Battle for H-3
Aerial clashes over western Iraq, on 6 and 7 June 1967, followed by a summary of operational history of Hunters in Iraq and Jordan, in period 1958-1967.

There's a total of 8 tables, including those listing all of Iraqi and Jordanian Hunters (and their fates), all the known attrition, all known COs of Iraqi Hunter Squadrons in that period etc.

Colour section is including a 'full pictorial walk-around' of the Hunter F.Mk.59A found at the junkyard of former Habbaniyah AB, in Iraq, and 16 artworks.

As always, any questions and/or commentary are most welcome.

01-26-2018, 08:01 AM
The next volume of the Middle East@War series to get published will be the part 3 in the Iran-Iraq War mini-series.

Primary topic of this volume remains the southern front of the Iran-Iraq War. Specifically, the volume is providing particularly detailed descriptions of the final large-scale Iranian offensives of 1987 and then the Iraqi counter-offensives of 1988. As far as I can say - and despite the publication of numerous related books over the last, say, 5-6 years, this will be the first ever to tell the 'full story'. Prepared with help of new documentation from Iraq, USA, and Iran, and in cooperation with multiple veterans from both sides of this conflict interviewed over the years, plus colleagues in the USA, Israel, and Iraq, it offers the following content:

Chapter 1: Iran’s Last Chance
Operations Kerbala-4, -5, and -8, which were the final IRGC-run attempts to break the backbone of the Iraqi army and capture Basrah, in 1987.

Chapter 2: Two Armies
The - meanwhile 'usual' - 'review' of the strategy, tactics, status, equipment, expansion, and 'everyday life' of both armies on the southern frontlines of this war.

Chapter 3: Saddam’s First Blow
Iraqi offensive on the Iranian-held Faw Peninsula, April 1988.

Chapter 4: Iranian Burn-Out
Emboldened by their success at Faw, the Iraqis launched another 'trial' offensive with the aim of liberating the Majnoon islets and surrounding areas.

Chapter 5: End Game
The final Iraqi offensives into Khuzestan of the summer 1988 have de-facto destroyed the Iranian military's ability to defend.

Of course, I'm biased, but...I would lie if stating anything else than this volume came out far better than ever expected - and that 'already' content-wise. Thanks to Ted's endless efforts, the results of an entire decade of research with help of a myrad of sources, literal 'millions of pieces of the puzzle' were put into the same volume, in a nicely sorted-out and beautifully narrated fashion. The volume bristles with ORBAT tables, very precise descriptions of involved commanders, units, geography, and the flow of specific operations. Thus, and although there is meanwhile plenty of literature about the Iran-Iraq War, this work offers an exclusively precise insight.

Simplest description: this is exactly the kind of book about Iran-Iraq War I always wanted to read.

Distribution of this volume is to start the next week.

Attached bellow are the final cover and a few 'specimen pages'.

01-28-2018, 04:14 PM
The Gulf War: The Origins and Implications of the Iraq-Iran Conflict (https://www.amazon.com/Gulf-War-Implications-Iraq-Iran-Conflict/dp/0195045297/ref=sr_1_1?ie=UTF8&qid=1517155241&sr=8-1&keywords=The+Gulf+War%2C+The+Origins+and+Implicati ons+of+the+Iran-Iraq+Conflict%2C)

Iran-Iraq War: The Political Implications (https://www.amazon.com/Iran-Iraq-War-Political-Implications-Adelphi/dp/0860791130/ref=sr_1_1?s=books&ie=UTF8&qid=1517155301&sr=1-1&keywords=Iran-Iraq+War%3A+The+Political+Implications)

Iran Iraq and the Legacies of War (https://www.amazon.com/Iran-Iraq-Legacies-War-Potter/dp/1403976090/ref=sr_1_1?s=books&ie=UTF8&qid=1517155480&sr=1-1&keywords=iran+iraq+and+the+legacies+of+war)

The Iran-Iraq War (https://www.amazon.com/Iran-Iraq-War-Twentieth-Century-Wars/dp/0230577741/ref=sr_1_fkmr0_1?s=books&ie=UTF8&qid=1517155657&sr=1-1-fkmr0&keywords=iran-iraq+wardrobe+johnson)

The Lessons Of Modern War, Vol. 2: The Iran-Iraq War (https://www.amazon.com/002-Lessons-Modern-Vol-Iran-Iraq/dp/0813313309/ref=sr_1_1?ie=UTF8&qid=1517155742&sr=8-1&keywords=The+Lessons+Of+Modern+War%2C+Vol.+2%3A+Th e+Iran-Iraq+War)

The Iran-Iraq War. Volume 1: The Battle For Khuzestan, September 1980-May 1982 (https://www.amazon.com/Iran-Iraq-War-Khuzestan-September-1980-May/dp/1911096567/ref=sr_1_1?s=books&ie=UTF8&qid=1517155786&sr=1-1&keywords=The+Iran-Iraq+War.+Volume+1%3A+The+Battle+For+Khuzestan%2C+ September+1980-May+1982)

The Iran-Iraq War. Volume 2: Iran Strikes Back, June 1982-December 1986 (https://www.amazon.com/Iran-Iraq-War-Strikes-1982-December-Middle/dp/1911096575/ref=pd_bxgy_14_img_2?_encoding=UTF8&pd_rd_i=1911096575&pd_rd_r=D3FAQS0P0XK04HXCHFRG&pd_rd_w=ZIuV4&pd_rd_wg=wuKda&psc=1&refRID=D3FAQS0P0XK04HXCHFRG)

The Iran-Iraq War: A Military and Strategic History (https://www.amazon.com/Iran-Iraq-War-Military-Strategic-History/dp/1107673925/ref=sr_1_1?s=books&ie=UTF8&qid=1517155859&sr=1-1&keywords=The+Iran-Iraq+War%3A+A+Military+and+Strategic+History)

The Iran-Iraq War (https://www.amazon.com/Iran-Iraq-War-Pierre-Razoux/dp/0674088638/ref=pd_sim_14_1?_encoding=UTF8&pd_rd_i=0674088638&pd_rd_r=M98V9HV9FJXYDXFX343P&pd_rd_w=TVtrt&pd_rd_wg=7R5e7&psc=1&refRID=M98V9HV9FJXYDXFX343P)

The Iran-Iraq War: New International Perspectives (https://www.amazon.com/Iran-Iraq-War-International-Perspectives-History/dp/1138831905/ref=sr_1_1?s=books&ie=UTF8&qid=1517155972&sr=1-1&keywords=The+Iran-Iraq+War%3A+New+International+Perspectives)

The Longest War: The Iran-Iraq Military Conflict (https://www.amazon.com/Longest-War-Iran-Iraq-Military-Conflict/dp/0415904072/ref=sr_1_2?ie=UTF8&s=books&qid=1212546737&sr=1-2)

01-29-2018, 12:21 PM
With the next volume of the Middle East@War going to the print, it's about the time to announce details of it, too.

This is going to be the - much expected, apparently - 'Iran-Iraq War, Volume 4: The Forgotten Fronts', i.e. the fourth band in this mini-series.

The volume is detailing operations on the central and northern frontlines of the Iran-Iraq War. These frontlines were actually decisive at certain points during this war, but only on something like 'temporary' basis. Therefore, most of foreign observers didn't even pay attention about them, and they received very little coverage even in official publications by both of involved parties. On the contrary, we went to extension to not only describe often complex geo-political backgrounds of these frontlines (mind: 'Kurds'), but can observe up front: to the best of my knowledge, we didn't miss a single operation undertaken by either party in this war, no matter how small.

Chapter 1 The Opening Operations
Essentially, this is the summary about the Kurdish uprising of 1979, and the Iranian (foremost: IRGC's) intervention in regards of the same, and then the Iraqi invasion of 1980.

Chapter 2 Private Wars
Although part of a greater struggle, many operations by both sides on the northern and central fronts had the characteristics of private wars. These were fought in a wide range of terrain and, unlike the big battles on the southern front, were characterized by the absence of a continuous line.

Chapter 3 The Central Front 1982-1987
In 1982, the central front - which was quite 'peaceful' already since October 1980, was re-activated by the Iranians who launched the Operation Fatah al-Mobin. This was - by far - the most successful offensive launched by the Iranian military during that war. In turn, it not only emboldened Tehran into launching dozens of such operations for the next five years, but also kept this frontline 'active' throughout this period.

Chapter 4 The Northern Front 1982-1987
Chapter 4 follows with a similar description of - mostly - relatively 'small action' on the northern frontlines in period 1982-1987.

Chapter 5 Iran’s Last Chance
Following the bloody failures around Basra (see Volume 3), and with the passing of Khomeini’s deadline for ‘final victory’ by 31 March 1987, the SDC reconsidered its strategic options. Finally concluding that taking Basra was extremely unlikely, it decided to switch the strategic focus northwards, and press deeper into northern Iraq with Kurdish support. A key factor for this decision was the existence of extensive areas – ‘sanctuaries’ – held by militants of the Kurdish PUK around Suleymaniyah.

Chapter 6 The Kurdish Front 1980-1988
Centrepiece of this chapter are Iranian operations into northern Iraq (Ops Fath-1 up to Fath-10 and Zafar-1 to Zafar-7), and then of Iraqi campaigns code-named Anfal (these went from Anfal-1 to Anfal-8). This was the hardest chapter of this book to write: lots of 'minor operations, small-unit action and similar.

Chapter 7 The Last Battles 1988
In June 1988, following success in the south, Saddam Hussein ordered a major offensive in the north too, with the aim of 'liberating Arab land from Persians', but also with the aim of mauling the Iranian military and rendering it non-operational. Thus came into being the planning for little-known, multi-corps Ops like Tawakkalna ala Allah-3 and -4, run in July 1988. Finally, once Tehran accepted the UN-mediated cease-fire, Saddam 'unleashed' the MEK/MKO (i.e. the 'NLA') into an attack on Kermanshah, in July 1988.

The book is illustrated by no less than 13 maps: point is that most of northern and central battlefields are little known, and require good maps for reader's easier orientation.

In regards of colour profiles, we've got two new artists for 'tanks'. One of them is Peter Penev from Bulgaria who already drew artworks of North-Korean-made Koksan SP-guns for Volume 3, and then continued with preparing 11 additional artworks for this volume. This is his first project of this kind, and his work is simply outstanding - in regards of details and precision in particular. Since we've had enough space, and have presented all the major types in service with both armies to extension in earlier volumes, I've asked him foremost to draw less-well-known heavy vehicles of this war (say, Yugoslav-made M60 APCs, or Brazilian-made EE-9 Cascavels, and then various self-propelled artillery pieces).

Overall, a volume that's nicelly rounding-up this mini-series.

Attached bellow are the final cover and a few 'specimen pages'.

01-03-2019, 05:15 PM
Interview with author Tom Cooper on the Iran-Iraq War http://musingsoniraq.blogspot.com/2019/01/the-iran-iraq-war-interview-with-author.html

01-03-2019, 07:10 PM
Excellent interview by Joel Wing and his post moved to this thread - which covers the historical Iran-Iraq War. This thread has been moved from the Middle East arena to the Historians arena. It has been re-opened fir any reaction.

01-11-2019, 04:34 PM
Book reviews of 3 of Tom Cooper's books on Iran-Iraq War as well that were mentioned earlier in this thread