Most of the fighting is being done by active duty troops, and most of the reserve (including National Guard) troops are in support jobs. Despite that, reserve troops are suffering nearly as many casualty as the active duty troops. The relatively high rate for National Guard and reserve troops is attributable to a number of factors. The main one is that they are less well trained. The army doesnt like to talk about this one, because the official word has always been that the part time soldiers are able to serve as effectively as their active duty brethren. But ever since the modern reserve system was invented in the 19th century, it has been common knowledge that the reservists are always less well prepared for combat. For most of the last two centuries, this was not a major issue. The reservists would take more casualties, be less effective, but would catch up after a few months of combat. In the United States, if was felt that, since most reservists are non-combat troops were, and would only be used in a major war, this would not be a problem. Reserve combat troops would eventually catch up in the experience department. Recently drafted men, trained for less than a year and sent into combat, usually suffered higher casualties as well. The whole point of having reserve troops was to have more trained military manpower on short notice. But its becoming an issue in Iraq. However, no one should have any doubts about why.
In addition to less training, the reservists also have equipment problems. Reserve units get new gear after active duty troops are taken care of. This is often remedied for troops headed for Iraq by issuing the reservists with the new stuff before they go. But this means the reservists are still getting used to the new gear. An attempt has been made to remedy this by giving the reservists months of additional training before shipping them out. This helps, but it does not completely solve the problem.
Another reason for the higher reserve casualty rate has to do with the unique nature of the Iraq operations. Most of the attacks on American troops are directed at troops in vehicles on the road. The Iraqi gunmen already knew, from experience in 1991 and 2003, that they could not expect to do much against American combat troops. So the Sunni Arab rebels rely on roadside bombs and ambushes. Most of the troops caught up in this are non-combat reserve troops, who are, along with active duty non-combat troops, taking higher casualties as a result. Most of the reserve combat troops have been assigned to guarding bases in Iraq. They have done very well at this, as one can see from nearly non-existent attacks on these bases (except for the mortars and rockets, which are not accurate enough to do substantial damage.)
Theres no easy solution for this situation. Additional training helps, but is unpopular with the reservists because it keeps them on active duty longer. The main reason for the gap between active duty and reserve troops is experience. Not just with the troops, but also with the officers. In fact, the reserves have long had an officer shortage. The reserve officers have a higher workload than the enlisted troops and its been increasingly difficult to get the number needed. As a result, reserve units are usually sent off to Iraq with a lot of last minute officer additions, scrounged up wherever they could be found. The lack of experience also extends to some of the NCOs, even through the National Guard has long had success in recruiting men and women who just finished three or more years of active duty.
What the army has done to address the problem is put a lot of effort into making the convoys better able to handle the attacks. But this does not get away from the basic fact that the reservists will always be at a disadvantage when it comes to training, experience and the ability to avoid casualties.
The army still takes the most casualties in Iraq, as has been the case with armed forces throughout history. Out of 1,235 troops killed (combat and accidents) in Iraq, the army has lost 858 dead, the marines 350, while the air force and navy combined have lost 27. For every 1,000 active duty army troops sent to Iraq, 2.64 have died. For the National Guard and reserves, about two soldiers have died for every thousand sent over. The marines, navy and air force send troops over for different length tours, so their death rates are not comparable. But the marine rate is probably closer to 3 per thousand, while the air force and navy rate is under 1. For every death, there are about eight more wounded or injured.