These foreigners will probably take to the usual tactics of terrorist groups. However, this may be difficult in Iraq, which does not have a tradition of radical Islam. There is some radical Islamic activity in southern Iraq, around the Shia holy cities of Najaf and Karbala. There is also a Iraqi rebel army of Shias in Iran, which will eventually come home. The leaders of this group oppose Americans being in Iraq and are influenced by Iranian Islamic radicals who support Hezbollah (Shia terrorists) in Lebanon. If terrorist groups cannot establish a base among a friendly population in Iraq, they will be easier to root out (as happened with Islamic terrorists in Egypt.) But in the mean time, the terrorist groups will be simultaneously trying to kill Americans and establish a base of support in Iraq.
In a Baghdad school, U.S. Marines found a large supply of equipment for suicide bombers. This included fifty vests, each fitted out with 20 pounds of explosives, plus ball bearings (to increase the casualties.) The vests were wired for use and only needed a battery, and someone to wear it. More suicide attacks are expected, but adapting successful Israeli tactics, American forces are aggressively chasing down the support staff that are needed to recruit, equip and send out the suicide bombers. Without that kind of support, there will be far fewer, if any, suicide attacks. Meanwhile, there are hundreds, perhaps thousands, of foreign volunteers in Iraq to fight Americans. Not all of these foreigners are terrorists, many see themselves as "mujahadeen" (holy warriors) fighting for Islam against infidels. Oddly enough, there were never any volunteers to overthrow Saddam, considered a murderous tyrant by all his neighbors, but here they are to defend him. However, this is the raw material from which al Qaeda was formed. Some of these groups appear to be concentrating on terrorism, as witness the suicide vests found by the marines. American Special Forces and Rangers guarding the roads from Jordan and Syria and are still catching young Arab men trying to enter Iraq and join the fight against Infidels. These guys are usually not carrying weapons, but often have lots of cash, and documents indicating their intentions. This indicates some degree of organization.