War is a large scale event comprising a number of battles, and involving one or more nations or establishments. A battle on the other hand is a rather small scale combat, which is usually localized. For example, World War Two was a war between the allied powers and the Axis Powers, while the Battle of Stalingrad was a battle between Nazi Germany and the USSR for control over the Russian city of Stalingrad.
In simplest term battle is subset of a war . war is fought on number of battle field together with each battlefield having a battle. for example in world war 2 there were battles like battle of Stalingrad,battle of Berlin, battle of imphal and many more