With the advent of Japan, a European war became a world war and this European war continued on three fronts. The largest front was in Russia where the Germans had conquered large tracts of land and threatened the great cities of Moscow, Leningrad and Stalingrad. The other two fronts, smaller in the use of manpower but not in territory, were in North Africa and the Atlantic Ocean. Japan changed all this and started a world war. Their ambitions were directed at control of the Pacific Ocean and south east Asia. Most of the latter was in the hands of foreign empires and the Japanese struck a chord with the object of taking the Philippines from the US, Malaya from the British and Indonesia from the Netherlands. This they did very quickly. During the winter the Germans were pushed back on the Moscow sector. They had to make a decision as to whether they wanted to take Moscow or Stalingrad and go into the Caucasus. German weakness was a lack of oil, so for the time being Moscow was safe. The Russians were learning fast how to wage war and they now retreated in good order and only fought the Germans from a position of advantage. In North Africa, the armies moved backwards and forwards until the Germans gained an ascendancy and came close to Cairo on the El Alamein line. However, they were exhausted and lost their mild but important air superiority. German tankers were being sunk in the Med and the Allies had found an able new commander. A great battle was fought at El Alamein. An Axis army was defeated and they never regained the initiative. The oil and food war was centred on the eastern American seaboard. The Germans had much success as the Americans did not use a convoy system for the Allied tankers. The attacks were only debilitating as the US were concentrating on getting their troops and supplies into North Africa. The great German objective was to starve Britain into submission and to interdict the oil supply lines which would stop the bombing of Germany In the Pacific, the Japanese wanted to form a defensive zone which stretched at its furthest borders from the Aleutians, the Hawaiian Islands, Fiji and onto Australia. The Japanese thought they could do this by winning a great naval battle which would give them control of the Pacific. The Japanese had a great fleet, superior to the Americans. The Battle of Midway as it became known, revolved around the carriers and their aircraft and pilots. There were four Japanese carriers and three American. The four Japanese carriers were sunk while the Americans lost one. The Japanese air arm was savaged. The battle was truly decisive although the Americans only took control of the western Pacific.