In 1941, The Brits decided that it was time for their boys to take the war to the enemy, and for Fighter Command it meant what became known as "Rhubarb Raids". Leaving the boys home to rest on their arse was not in the cards for these recent heroes of the Battle of Britain. At least 2 or more aircraft to a raid, they would look for ground targets mostly, and harass the enemy any way they could. These raids acquired another purpose later on in 1941, which was to draw Luftwaffe fighters to France, relieving pressure on the Russian front. Helping the Russians was a good thing for the Allies, as in the end, they bore the brunt of the fighting. The Allies relationship with the Russians haven't gone so well since the war ended.
The raids were hard on the fighter crews, getting down on the deck to bomb or strafe something put the aircraft at serious risk, German anti-aircraft crews were the best in the world, and large numbers of planes and pilots were lost. Other dangers included the same dangers faced by German crews during the Battle of Britain, the planes were at the edge of their range usually during a fight, and they had to cross the channel twice, the second time with the possiblility of already being damaged or shot up during the Rhubarb. The German planes they faced were better, later variants of the Bf109, and then the FW-190. Of course this arms race had already been going on, and the Spits got better too.
One of the Spitfire pilots lost on a Rhubarb was Robert Tuck, a veteran pilot with 29 kills to his name. Not so much a natural when he first climbed into a plane, during the war he learned fast and became an ace in less than 24 hours over Dunkirk. In the end, Tuck and his buddy shot up a locomotive over France and was nailed by German antiaircraft. Never one to forgive who shot at him, Tuck shot up a mobile AA gun before crashing. Having killed some of the crew, he realized he was a done chump when captured by the AA crew. Luckily, they were amazed one of his 20mm cannon shells had gone down one of the barrels of their gun, splitting it open.... they didn't kill him.