He attended the Royal Military College, Sandhurst and, after graduating from there, was commissioned as a second lieutenant into the Welch Regiment of the British Army in September 1912.
[9] In August 1916 Lomax was appointed second-in-command of the 20th (Service) Battalion, Manchester Regiment, a Kitchener's Army unit, which came with the rank of temporary major.
[9] He had also been awarded the Military Cross (MC) in January 1917,[13] as well as the Distinguished Service Order (DSO) for his actions during October 1918, when the war was coming to its end.
[25] From March to October 1938, Lomax also commanded of the Delhi Independent Brigade Area with a local rank of brigadier.
[28][9] In September 1940, a year after the Second World War began, Lomax's brigade was sent to Egypt to join the Western Desert Force.
[2] The 16th Brigade was ordered forward in mid-June 1941 as reinforcement to the forces advancing north against Vichy-controlled Syria and Lebanon.
During Operation Crusader the brigade's battalions were involved in the break-out from Tobruk to link with the 2nd New Zealand Division on the night of 26 November.
[31] In February 1942, following the Empire of Japan's entry into the war on the side of the Axis powers, the 70th Division was ordered to India to bolster its defences.
The 16th Brigade set off in March but following the fall of Singapore the previous month, the Royal Navy's most important remaining base in the East at Trincomalee in Ceylon was felt to be under threat from the Japanese and the brigade was diverted to Ceylon where it was attached to the 34th Indian Infantry Division.
[31] Finally Irwin introduced Indian XV Corps headquarters under Lieutenant-General William "Bill" Slim to take control.
[33] Slim later wrote of Lomax: Never had a divisional commander, immediately on taking over a strange formation, in a new type of war, been confronted by a more desperate situation.
The Fourteenth Army commander had anticipated this and ordered that the forward divisions should fight where they stood and be supplied by air.
His final assignment was as President of the No.1 Commissions Board, relinquishing the appointment in August 1949[37] and retiring from the army the following month.