In which war was the Avro-Lancaster bomber plane used?

The Avro Lancaster is a British four-engined Second World War heavy bomber. It was designed and manufactured by Avro as a contemporary of the Handley Page Halifax, both bombers having been developed to the same specification, as well as the Short Stirling, all three aircraft being four-engined heavy bombers adopted by the Royal Air Force (RAF).

A long, unobstructed bomb bay meant that the Lancaster could take the largest bombs used by the RAF, including the 4,000 lb (1,800 kg), 8,000 lb (3,600 kg) and 12,000 lb (5,400 kg) blockbusters, loads often supplemented with smaller bombs or incendiaries. The "Lanc", as it was known colloquially, became one of the most heavily used of the Second World War night bombers, "delivering 608,612 long tons of bombs in 156,000 sorties".