The p51 is an iconic fighter that filled a vital role in WW2 Europe. American bombers including the b17 flying fortress and b24 liberator were pounding German cities later in the war. They were suffering heavy causalities inflicted by defending fighters of the Luftwaffe, such as the fw190. The escorting fighters available like the p47 were not able to accompany the bombers all the way to the target and back due to limited fuel.
The p51 was armed with 6 .50 caliber machine guns, 3 in each wing.
The p51 was designed to carry enough fuel to make the entire voyage with the bombers. When fitted with the British merlin engine used in the spitfire it was an outstanding performer at high altitudes. It was more than a match for the bf109 and a match for the fw190. The Luftwaffe suffered heavy losses when attacking the bombers. The Germans could not replace the experienced pilots lost and newly trained ones were easy pickings for the American pilots.
Mustangs encounter a flight of bf109's.