 The squadron re-equipped with the Wellington Mark XIII and the rate of sorties increased, although the aircraft losses also increased as they were hunted by German night-fighters in the Western Approaches.The Wellington Mk XIII and later XII and XIV have been described as 'the prototype for AWACS' and 172 squadron is renowned for being the first to attack a U-boat at night using the combination of ASV and the Leigh Light.This first attack came on 4 June 1942.