When al Qaeda leader Abu Musab al Zarqawi was killed four weeks ago, enormous damage was done to his network of Iraqi, and foreign, terrorists. The foreigners turned out to be an interesting bunch, who fell into two categories. Most of the suicide bombers are foreigners. Suicide, even for religious purposes, is just not that popular in Iraq. So foreigners are used for much of that work. But the other type of foreign terrorist is even more dangerous. These are the terrorist leaders, who have been coming to Iraq because it's where the action, and money, is. Also, Iraq tends to be safer for Islamic terrorists than any other place in the world. Islamic terrorists have lost most of the refuges they used to enjoy in places like Saudi Arabia and Algeria. Even Jordan is now largely anti-terrorist.
In Iraq, the terrorist partnership with Saddam's old Baath Party secret police forces, continues to function. Despite the disagreement over al Zarqawi's use of terrorist attacks against Moslems, the al Qaeda/Baath alliance still has the same goal, getting the foreign troops out of Iraq, and putting Sunni Arabs back in control. The information captured from Zarqawi's hideout, and subsequent raids, provided a better picture of how many foreign terrorists were in Iraq, and what they did. Previously, most information about the foreigners came from identifying the dead suicide bombers, and interrogating the few foreigners taken alive. But when Zarqawi went down, a lot (about 60 so far) of mid and upper level foreign terrorists got killed or captured. More documents were taken as well.
It turned out that the foreigners provided two important functions. First, the foreigners had experience with operating while being pursued by police and military forces. The Baath Party thugs had been terrorizing Iraq for decades without police interference. That's because the Baath bully-boys were the police. But after 2003, it took the secret police, now transformed into terrorists (or "freedom fighters", depending on where you get your news), a little while to adjust to the fact that they no longer had police powers. The foreign al Qaeda men showed the Baath boys how to avoid unpleasant encounters with the Americans, or the growing Iraqi security forces. The foreigners had all sorts of practical tips, and they were grateful for the sanctuary they found in the Sunni Arab towns and neighborhoods. There, the foreigners also discovered that they were rather more honest and trustworthy than their hosts. Saddam's "republic of fear" had, over the years turned into a nation of thieves and liars. The more extreme police states tend to do that. So the foreign terrorists were increasingly entrusted with the money being moved into the country to finance terror attacks. Saddam and his cronies had stolen billions of dollars from Iraq's oil wealth, and in early 2003, a lot of that was just sitting around, inside opulent palaces, in the form of U.S. hundred dollar bills, or large denominations of other currencies (especially euros.) This cash, and millions more brought in from foreign banks, was often moved and disbursed by the foreign terrorists. That way, less of it got stolen before it could be used to pay the foot soldiers of the terrorist campaign (who made the bombs, planted them, set them off, and carried out ambushes and murders).
There were never that many foreign terrorists in Iraq, and most of them came to die as suicide bombers. But the non-suicidal ones made themselves really useful, and dangerous.