After the 3rd Division, to which the 33rd Battalion was assigned, deployed to the Western Front in November 1916, Cartwright served with them through the Battle of Messines where he was wounded in June 1917. Later, in April 1918, he was wounded again when the 33rd Battalion's position was attacked with gas while holding a position around Villers-Bretonneux. He was briefly hospitalised but returned to duty in June. In August, the Allies launched the Hundred Days Offensive around Amiens, which resulted in a series of advances as the Allies sought to break through the Hindenburg Line.