Ypres Salient for several months from February 1915. In an action at Kemmel on 24 April 1915, a trench he was in was bombed. Although wounded, he organised the defence and rescued buried men under heavy fire. He refused to leave his post until ordered to by his superiors. He was promoted to lieutenant on 26 April 1915 and two months later was made a temporary captain. Vann further distinguished himself in fighting at Hooge in late July to early August, assisting another officer in holding the line and leading patrols to the German trenches, gathering intelligence. For his actions over this period, he was awarded the Military Cross (MC). On 25 September 1915, his brother Arthur was killed at the Battle of Loos. The following month, Vann was wounded during fighting at the Hohenzollern Redoubt which resulted in him being sent to England for treatment. He returned to the front in June 1916, his captain's rank having been made substantive. He soon was promoted to acting major. In August 1916 Vann received a bar to his previously awarded MC "for conspicuous gallantry in action. He led a daring raid against the enemy's trenches, himself taking five prisoners and displaying great courage and determination. He has on many previous occasions done fine work." Later in the year, suffering neuritis in his neck, he was sent to England for medical treatment. Declared fit in March 1917, he was sent on a command training course and returned to the front six months later as commander of 2/6th Battalion Sherwood Foresters. During this time, he was awarded the Croix de Guerre. He was promoted to acting lieutenant colonel the following month. On 27 December 1917, at St Paul's Church, Knightsbridge, he married Doris Victoria Strange-Beck, a Canadian nurse working at a hospital in England. For the first part of 1918, Vann spent periods in hospital or on leave. In June 1918, Vann took over command of 1/6th Battalion Sherwood Foresters. On 29 September 1918, during the Battle of St Quentin Canal, he led his battalion across the canal through thick fog and under heavy fire. He secured his troops' advance by rushing up to the firing line and leading the advance forward himself. Of his battalion, nearly 30 men were killed and over a hundred others were wounded in this engagement. A few days later, on 3 October 1918, he was again leading