http://www.dtic.mil/cgi-bin/GetTRDoc...f&AD=ADA509378

Where Are the Infantry Sergeants: An examination of the Marine Corps' policies and processes that adversely affected the availability of infantry sergeants to serve as squad leaders in the operating forces - Major Thomas M. Tennant

This is another thesis paper submitted for a military studies masters degree requirement at the Marine Corps Command and Staff College. The historical section that details the history of the squad leader has a lot of researched detail about the employment of squad leaders as far back as the AEF in WWI.