Ninety percent of the foreign fighters enter through Syria, according to U.S. intelligence. Foreigners are some of the most deadly fighters in Iraq, trained in bomb-making and with small-arms expertise and more likely to be willing suicide bombers than Iraqis. Foreign fighters toting cash have been al-Qaida in Iraq's chief source of income. They contributed more than 70 percent of operating budgets in one sector in Iraq, according to documents captured in September 2007 on the Syrian border. Most of the fighters were conveyed through professional smuggling networks, according to the report.
