After military college, Vane was assigned to the
Worcestershire Militia,
Scots Guards and the
Submarine Mining section of the
Royal Engineers over the period of 1883-1888. In 1886, he began residing at
Toynbee Hall in East London. That year he started a 'Working Boys Cadet Corps'. He became a captain in the 26th Middlesex
Rifle Volunteers in 1888. While serving in the
Second Boer War (1899–1902), he was appointed a
magistrate in 1902. He was removed from that position for supposedly being too "pro-Boer". During the
Easter Rising, Vane distinguished himself for his courageous conduct in handling of abuses by an officer under his command, Captain John Bowen-Colthurst, who had ordered three unarmed civilians shot to death, and had himself killed an unarmed teenager. Vane had been directed to take command of the defence of
Portobello Barracks, Dublin, then garrison for the largely Belfast-recruited
Royal Irish Rifles and the Ulster Militia Battalion. On the third day of the rising, Vane had taken up an observation position in the tower of the
Rathmines Town Hall. On returning to barracks, he learned that civilian hostages had been taken and later killed there by order of Captain Bowen-Colthurst. They included the well-known pacifist
Francis Sheehy-Skeffington and two pro-Union journalists who were misidentified as Nationalists. Bowen-Colthurst had also led a raid against a house allegedly sympathetic to the insurgents, and during this raid he had summarily executed a youth, James Coade, in the street. Vane ordered these incidents to be reported to the garrison high command and to the British high command. But his superiors covered up the crimes, and removed him from command. Thereupon Vane went directly to London and met with Secretary of War
Lord Kitchener and with
Maurice Bonham Carter,
Principal Private Secretary to the Prime Minister, to expose the murders. As a result, Bowen-Colthurst was arrested a week after the rising, and was charged with murder at a
court-martial held a month after the rising. The court-martial found Bowen-Colthurst guilty, but insane; he was sent to
Broadmoor Hospital for the criminally insane. Nevertheless, Vane's superior
Sir John Maxwell filed an adverse report about Vane, resulting in Vane's dismissal from the army sometime prior to August 1916. ==Between periods of military service==