So many Japanese planes were lost that the Port Moresby invasion force, without adequate air cover and harassed by Allied land-based bombers, turned back to Rubal. The four-day engagement was a strategic victory for the Allies.
First of all... what period? because if you are talking about this time, I think it is becaise they want to feel powerful to be able to have more allied countries in any situation, they also do it because they want to control most of the world natural sources that other countries have.
