Iraq is suffering through one of the most intense car bomb campaigns seen in years. Before the Islamic State would have gaps of up to a week between VBIED series. In August there has only been one day in between the waves. IS probably stockpiled explosives before their summer offensive started, but then their capture of so many ISF bases has probably given them access to a huge new amount of artillery and mortar shells, etc. which helps explain why the car bombs are coming so intensely in recent weeks. Here's a link to the article.