The koran only permits war in self defence?

A muslim walking outside medina got lost one day and got attacked my a non muslim who nicked his wallet. He went back to mecca and told mohammed what happened. So mohammed sent his army to find this mugger. First they tried mecca, no sign of him, then arabia still no sign. So they tried syria jordon israel....where could he be..persia..north africa...no? well since we are in north africa why dont we pop over to spain and look.... No where could he be??? So off they went to seach turkey and eastern europe. Doh! They lost him. Where next?