Different prerequisites for war exists and varies due to the terrain. Cities, mountains and covered terrain all creates their special conditions for the battle. The biggest difference in methods is found between the urban warfare and all the other ways of fighting in war. Combined arms constitutes the fundamentals of fighting a war, and organizing armed forces. But if the environment of the war is changing, the different prerequisites of combined arms need to change. The purpose of this study is to survey the distinguishing differences and prerequisites between the two kinds of environments, described in the invasion and fight in Rumaila oil field (2003) and Operation Phantom Fury (2004). By analyzing these cases, the purpose of this theory consuming case study is to explore and examine the use of combined arms in different environments during the Iraqi war in between 2003 and 2004. The analytical results reveal that the prerequisites before Operation Phantom Fury that made the operation successful was premonition to all the civilians in the city of Fallujah, the aggressive and massive use of indirect fire support, the reorganization of the divisions backbone, infantry, and finally the knowledge from earlier operations in Fallujah.