In May 1939, Monnington joined the Directorate of Camouflage at Leamington Spa where he worked on camouflage designs for airfields and factories. In 1943 Monnington, who had taken flying lessons before the war, wrote to the War Artists' Advisory Committee, WAAC, complaining of the lack of an aerial perspective among the works WAAC had so far commissioned. In November 1943, WAAC issued Monnington with the first of a series of full-time commissions that saw him flying with a training squadron in Yorkshire and with Mitchell bombers to Germany. The winter of 1944-1945 was spent in the Netherlands amongst the Second Tactical Air Force drawing mobile radar and radio units. Monnington was naturally drawn to subjects of a technical nature.