"Anyone following the casualty reports out of Iraq over the last six months will notice that the conflict is becoming steadily more deadly for both Iraqi civilians and the U.S. military. The increase in casualties is in part the result of the upsurge in sectarian violence in Baghdad and other cities, where American troops are increasingly vulnerable to guerrilla tactics favored by the insurgents and the anti-U.S. Shiite militias. But there is another reason why more U.S. military personnel are being killed and maimed: The insurgents and militias are fielding a new array of dangerous conventional weapons. While the Sunni insurgents mostly continue to use the leftover equipment and ammunition from Saddam Hussein's ammunition dumps, the Shiite militias are seeing their weapons upgraded and improved courtesy of Tehran and Moscow. There are even rumors of Iranian arms deliveries to Sunni insurgent groups."
Naval Postgraduate School, Center for Contemporary Conflict: http://www.ccc.nps.navy.mil
Strategic Insights (March 2007), v.6 no.2