The 20,000 marines going to Iraq, to relieve army troops, have carefully studied their own earlier experience in Iraq, and that of the army, and prepared themselves for a different form of combat than they encountered in early 2003. This time around, the marines will be inside Sunni Arab territory, where most of the violence is found. Last time around, the marines were in largely Shia areas, where there was a lot less hostility. Preparations this time around include Iraqis, or Iraqi-Americans, lecturing all marines on Iraqi customs and what to do and say to maintain good relations, and avoid accidentally insulting anyone.
Army advisors showed what they had learned about convoy operations in Iraq, and all marine trucks will have armor protection against ambushes and roadside bombs. The army is leaving some of its armored hummers behind for the marines, as well as some other equipment, and lots of files on army operations and techniques. The army has been turning over all its information on local contacts and a marine advance party went over early to meet some of those contacts and get a better sense of what the situation is. All marine helicopters will have anti-missile countermeasures and all troops will have the bullet proof protective vests.
The marines have more institutional experience at this kind of peacekeeping than does the army and are eager to use the tried and true marine techniques (which can be found at http://www.smallwars.quantico.usmc.mil/sw_manual.asp.)