His name appears in the first Gazette of the 1/1^st Huntingdonshire Cyclist Battalion printed in the winter of 1914 as a Major.   By 9-10-1914 at Filey, where they patrolled the coast he was a Captain in charge of A company.

7/8/14 - Good - Bye - Territorials leave Huntingdon.  Since the beginning of the week the headquarters of the Hunts Cyclist Territorials at Huntingdon has been seen of the greatest activity, and many recruits were accepted. The whole of the two Huntingdon companies were paraded on Tuesday evening, and again on Wednesday previous to the church parade. Further equipment, including trenching tools - a sort of combination of small pick and spade - was issued, and the whole of the men and their equipment were carefully inspected. Early this (Thursday) morning they were paraded and Marched to the Huntingdon Great North Region Station, ready for conveyance to their appointed station. Soon after 8.00 the railway station was surrounded by a large crowd. The Earl of Sandwich, in uniform, arrived by motor, and Mrs. Howard Coote and party were present in their car and Mrs. Barkley had also driven to the station. At 8:30 the train arrived, partly filled by the St. Neots contingent, under Lt. K. Hunnybun. The engine drew out and coupled on to the luggage vans standing in the dock and these were backed onto the front of the train. Meanwhile the two Huntingdon companies had arrived singing loudly and had been welcomed by cheering from the crowd. Safely in the trying the greater part of the "terriers" removed their coats, while at least two heads were hanging out of each open window and other faces were pressed against the glass. The shunting of the luggage was not yet complete and the interval was spent in the singing of "are we downhearted?" And popular songs learnt at Skegness during the recent camp and the shouting of "good - byes" to relatives and friends, who were either lining the railings of the up platform, or standing on the down platform at the carriage doors. At 8:40, when the train began to move, handkerchiefs were waved from the windows and both soldiers and crowd re doubled their cheers, which were continued until last of the train had passed under the bridge. The officers in charge were Captains M. Barkley, and A. R. Lowe, and Lieuts. J. M. S. Gardner, while Captain Cook joined the battalion later.

From a local paper dated 28/7/1916  Monday's "Gazette" contained the following:- Hunts. Cyclist Battalion: Captain (temporary Major) M. Barkley to be Major (May 13).

He was promoted to a Major in the Huntingdonshire Cyclist Battalion, from the rank of Captain, by 9th January 1915. This was announced in “The London Gazette”. He was Captain (temporary Major) made Major circa July 1916. ref A = Major by 12/12/1914. By the 9/6/1917 he had returned to light duties and was to remain at that state for 2 months, he held the rank of  Major.  Major by July 1916.

Lieutenant Colonel M. D. Barkley - Under Battalion orders, issued by Lieutenant Colonel M. D. Barkley, officer
commanding 2/1st Huntingdonshire Cyclist Battalion issued at Beechlands, Skegness on 5th July 1918, and signed by W. J. Satchell (Captain and Adjutant), on 4th July 1918 at 7-00 p.m., records indicate that he was detailed to appear before a Medical Board assembled at 'Waverley', Sutton-on-Sea, on Thursday, 4/7/1918 at 2:00 pm.

Lieutenant Colonel M. D. Barkley - Under Battalion orders, issued by Lieut. Col. M. D. Barkley, Commanding Officer, 2/1st Huntingdonshire Cyclist Battalion issued at Beechlands, Skegness, on 3rd August 1918 at 1:00 p.m., and signed by W. J. Satchell (Captain and Adjutant), orders being for the following day i.e. 4th August 1918, records indicate that he was granted leave of absence from 9/8/18 to 15/8/18 inclusive.

In 1920 he was Lieutenant Colonel commanding officer of the Huntingdon Territorial Battalion. His previous service had led him to the Boer war in South Africa with the Gloucestershire Yeomanry, he was badly wounded and sent home. During his time in South Africa he was also associated? / transferred to the Wiltshire Yeomanry.

He had retired by July 1926.