A series of air battles between Britain and Germany fought over Britain. After the fall of France, German aircraft launched a bombing offensive against British coastal shipping with the aim of attracting and then destroying British fighter aircraft, as a prelude to a general invasion of Britain. This action (July–August 1940) resulted in heavy German dive-bomber losses. Attacks were then made on southern England, but German losses were again heavy. In late August and early September mass bombing raids took place on British aircraft factories, radar installations, and fighter airfields; these caused heavy British losses, but Hitler ordered the offensive to be diverted to British cities just as RAF Fighter Command was exhausting its reserves of machines and pilots. Hitler’s priority of the day-bombing of London gave time for Fighter Command to recover. On 1 October day-bombing of major cities was replaced by night-bombing, but by this time it was clear that the major German objective, to destroy British air power, had failed. On 12 October Hitler postponed indefinitely his plan to invade Britain. Though heavily outnumbered by the Germans, the British lost 900 aircraft against 1,700 German losses. Radar, used by the British for the first time in battle, made a significant contribution.