When war broke out, Hartley was commissioned as a Lieutenant, joined the Canadian Infantry Battalion the 131st Westminsters and was posted to the Western Front.
In the Introduction to Thomas's WW1 collection of poems, S.W. Dyde, who was at the time the Principal of Queen's Theological College, Kingston, Ontario, Canada, gives us a little information about Hartley:
"When the war broke out young Hartley was just eighteen, and was taking an honors course in History andPolitical Science in Queen's University at Kingston. He enlisted immediately, only to find himself unfit. Thereupon he settled down to take his officer's training, and was at once given the position of war editor of the Regina Province.
After this experience in journalism, he taught school in a settlement of Germans and Swedes in southern Saskatchewan until he became fit for service. Then going home to Vancouver, he was given a commission in the 131st Westminsters, and, at the outbreak of the Somme offensive, was one of a special draft of officerssent forward. Thus he served with the Western Scots, and in one of his last poems, 'The Pipes o' War', can be seen the pride he took in his Highland regiment. He was proud of Highland blood, and the tartans meantmuch to him.
After the taking of Vimy Ridge he was transferred to the Royal Flying Corps, enthusiasm for which had long filled his letters. He was soon flying with Sir Julian Byng's army and shared in the adventures of the Cambrai offensive. Of course the usual share of mishaps and excitement came to him, and on one occasion during the Cambrai affair he and his comrade, as they crashed, had no hope of ever enjoying another meal save in a German camp. But they found their way back, and a reminiscence of this and similar common experiences, is found in the Moriturus Ego. Mainly engaged in the work of artillery observation, he gives a glimpse of the less known task of the air service in The Song of the 'Contact Patrol'".
After the war, Hartley became a Professor of History at the University of Western Ontario. Hartley died in 1970 and was buried in Woodland Cemetery, London, Middlesex County, Ontario, Canada – Grave ID 213997980. 
THE SONG OF THE CONTACT PATROL by Hartley Munro Thomas
THERE is war in the air! We go
Where bullets are swift and low,
(But we have bullets and bombs as well)
Into the path of the storm and shell.
Bullet for bullet, and bomb for bomb,
From Nieuport Bains to beyond the Somme,
We hurl from our dizzy machines
That is what warfare means
For them who make war in the air.
There is war in the air! We fly,
And sooner or later, die;
For we are trustful of flimsy wings,
Trustful of engine and "prop" that sings
Bullet for bullet, and bomb for bomb,
From Nieuport Bains to beyond the Somme.
And, Oh! that the people be true,
Who make us our planes anew,
Yea, they must be true to the air.
There is war in the air! We go
Though clouds and the rain are low.
For we have duty beyond the guns,
Bringing the curse of the air on the Huns
Bullet for bullet, and bomb for bomb,
From Nieuport Bains to beyond the Somme.
And, Oh ! that the people be wise
Who plan for the war in the skies,
For we must wage war in the air.
There is war in the air! We fly:
Both storm and the foe are nigh.
But we have many a shot to fire,
Diving from cloud to the edge of the mire
Bullet for bullet, and bomb for bomb,
From Nieuport Bains to beyond the Somme,
For each we have given two ;
And better, for all we do,
Is still to wage war in the air.
Painting: "Somme Contact Patrol" by modern artist Graham Turner.
Accurate aerial reconnaissance warned armies of impending attacks, kept officers informed of the position of friendly troops, etc. To ensure this both aircraft and kite balloons performed “contact patrols,” and were adapted to control the range of artillery guns.
Sources:
"Songs of an Airman and other poems" was published in 1918 by McClelland, Goodchild and Stewart, Toronto and can be read on-line here
https://archive.org/stream/songsofairmanoth00thomuoft#page/6/mode/2up
See also "We wasn't pals: Canadian Poetry and Prose of the First World War" edited by Barry Callaghan and Bruce Meyer and published by Exile Editions, Ontario, Canada, 2001
"Canadian Singers and Their Songs (1919)" edited by Edward S. Caswell Edward Samuel Caswell
(1861–1938) and
http://www.canadiangreatwarproject.com/searches/soldierDetail.asp?Id=150694
https://www.findagrave.com/memorial/213997980/hartley-munro-thomas
Photo: Hartley Munro Thomas from https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgGQRPDrXT8dDwnIjm6S2sAletkDkwSejdfQGpMFkyCklG3p_R12tzd4y3unMuYDQof51luqejMGtY8OvuXMLZ4AecGKVMhs9RMkft7_FsFrvBM2ipYBhHy4tPRuacKrmFya_ajGQCoa3g/s1600/Hartley+Munro+Thomas.png
Painting by Graham Turner from: https://www.studio88.co.uk/acatalog/Somme_Contact_Patrol_painting.html
I have been unable to find out more about Hartley Munro Thomas. If can anyone help please get in touch.
