 Tens of thousands of Iraqi soldiers dug-in along the front, backed by tanks and heavy artillery, while the Iraqi government established a blockade of food, fuel, and other goods to the area.The U.S. Air Force continued to enforce a no-fly zone over northern Iraq since March 1991, to defend Kurds fleeing their homes in northern Iraq, the U.S. military also built and maintained several refugee camps in 1991.This general stalemate was broken during the 1994–1997 Iraqi Kurdish Civil War, when due to the PUK alliance with Iran, the KDP called in Iraqi support and Saddam sent his military into Kurdistan, capturing Erbil and Sulaymaniyah.