He served with the Lovat Scouts. He kept a sort of diary for a while and he mentions where he went etc. Some of it is quite difficult to read but he was in Egypt, Greece, Belguim.
How fortuitous........The 1/1st Lovat Scouts and 2/1st Lovat Scouts along with the 1/1st Fife & Forfar Yeomanry formed the Highland Mounted Bde which sailed on the HMT Andania (Cunard Line) from Devonport on 8th Sep 1915 to Alexandria.
On the way the men were inoculated for cholera on 10th Sep 1915. HMT Andania anchored at Malta for a day on 14th Sep 1915 and after disembarking the Medical Officer of the 2nd Lovat Scouts (sick) at Valetta they then sailed on the 15th to Alexandria and the men had their second innoculation against cholera on board on 16th. They arrived at Alexandria on 18th Sep 1915 where excess baggage and transport was unloaded. On the 19th the men were disembarked and conducted a route march. On 20th they were issued infantry webbing and that evening sailed to Gallipoli, arriving at Lemnos Island at Mudros Bay on 23rd Sep 1915. The men were allowed ashore on 25th. Having transhipped to the SS Abbasieh they made it to Suvla Bay at Gallipoli on 26th Sep 1915.
The 1/1st Lovat Scouts, the 2/1st Lovat Scouts and the 1/1st Fife and Forfar Yeomanry war diaries are all available online from the National Archives. Interestingly the Lines of Communications War Diaries record the Andania arriving on Thursday 23rd Sep with the Highland Mounted Bde along with the Montana (an ammunition ship) with details of the 2/3rd London Regt and reinforcements for the 10th, 11th and 13th Divs. etc
I think it almost certain that the postcard is the HMT Andania given his unit sailed on it and it seems to have sailed either on it's own or with one other ship. Interestingly the 2/1st Lovat Scouts' War Diary implies that G and H Squadrons did not sail on the HMT Andania with the HQ Sqn and E Sqn plus the MG Section and the Signals Troop. The 1/1st Lovat Scout War diary for Sep is missing and the Fife and Forfar Yeomanry seem to be all on board the HMT Andania.
I hope this helps.
P.S. From my notes......
ANDANIA 1913 - The ANDANIA was a 13,405 gross ton ship, length 520.3ft x beam 64ft, two funnels, two masts, twin screw and a speed of 15 knots. There was accommodation for 520-2nd and 1,540-3rd class passengers. Built by Scott's Shipbuilding & Engineering Co, Greenock, she was launched for the Cunard Steamship Co on 22nd Mar.1913. On 14th Jul.1913 she sailed on her maiden voyage from Liverpool for Southampton, Quebec and Montreal. On 19th Aug.1913 she commenced her first London - Southampton - Quebec - Montreal sailing and in Jan.1914 started the first of three Liverpool - Queenstown - Portland - Boston sailings. She resumed London - Southampton - Quebec - Montreal service in Apr.1914 and between Oct.1914 and Mar.1916 was used as a troop transport. She resumed London - New York sailings on 18th Mar 1916 and on 31st Jan.1917 commenced her first Liverpool - New York voyage. She was torpedoed and sunk by the German submarine U.46 near Rathlin Light, Ireland on 27th Jan.1918 with the loss of 7 lives. [North Atlantic Seaway by N.R.P.Bonsor, vol.1,p.59][Great Passenger Ships of the World by Arnold Kludas, vol.2,p.16]