The biggest stumbling block for the Iraqis was the Battle of Khorramshahr. The Iraqis were unable to take it on the opening days of the war, and were forced to lay siege. The hold up  in this segment of the line would eventually stall their entire advance, and by the time they finally took the city in November after a bloody and protracted fight, they had lost much of their momentum, and the entire advance had begun to falter. By December, Saddam Hussein decided that his forces would dig in and simply aim to hold the captured ground. Trench warfare, dominated by artillery and airstrikes, took hold for the next few months.