Forbes volunteered for the Royal Naval Voluntary Reserve on 4th October 1914, soon after the war started. He was 5’7″ tall, with brown hair and grey eyes. But the navy had surplus volunteers and the army was short of men. Drake battalion was one of eight infantry battalions created to form the Royal Naval Division. Its first action was in the Gallipoli landings. Forbes was wounded in action on 11th May 1915 (gun shot wounds, upper arm), timing consistent with the Royal Naval Division landing at Helles, between the second and third Battles of Krithia. He was admitted to the Egyptian Government Hospital in Alexandria on 22 May. By 9th July 1915 he was at Mustapha Camp, Alexandria in Egypt and on 18th July embarked on HMT “Knight Templar” to rejoin his battalion. He later caught influenza and was invalided home on the Hospital Ship “Itonus” from Mudros harbour on 9th September 1915.

He found time when back in Britain to return to Forfar to marry Isabel Barry Fyfe McMath, also a schoolteacher, on 30th October 1915.

On 22 November 1915 he was in Blandford with the 1st Reserve Battalion and by May 1916, he was back with 2nd “Drake” battalion, “B” Company and was promoted to Leading Seaman on 6th July 1916. On 9th September 1916 he was transferred to Brigade Machine Gun Company. The 63rd (Royal Naval) Division had been sent to France in May 1916, and Forbes left from Depot Machine Gun Company, Grantham, on 24 November to join the Division on the front line. He was at the Machine Gun Corps Base Depot in Camiers on 12th February 1917, later transferring to 189th Machine Gun Company. The Division took part in the Second Battle of the Scarpe (23-24 April 1917), a phase of the Arras Offensive, capturing Gavrelle. But Forbes was reported killed in action on 24 April 1917.

He was a talented artist as shown by a painting (left) of his future wife, Isabel, signed and dated September 1913. Isabel married again in 1921, but kept the small image of Forbes in his naval uniform in her locket (right); both images kindly supplied by Emily MacMath.