Following the fall of France in 1940, Polish units were formed in the United Kingdom, as a part of the Royal Air Force and known as the Polish Air Force (PAF). Four Polish squadrons were formed: 300 Squadron and 301 Squadron flew bombers, 302 Squadron and 303 Squadron flew Hawker Hurricane fighters. The two Polish fighter squadrons first saw action in the third phase of the Battle of Britain in August 1940, with much success; the pilots were battle-hardened and Polish flying skills had been well learned from the invasion of Poland. The pilots were regarded as fearless, sometimes bordering on reckless. Nevertheless, success rates were very high in comparison to UK and Empire pilots. 303 Squadron became the most efficient RAF fighter squadron at that time. Many Polish pilots also flew individually in other RAF squadrons.