During the war, he joined the Royal Artillery as a gunner before being commissioned into the Royal Armoured Corps Officer Cadet Training Unit at Sandhurst. The Royal Military College had closed on the outbreak of war. He served with the 16th/5th Lancers, choosing that regiment because of its Irish heritage; the 5th had been the Royal Irish Lancers until 1922. In December 1944, he joined the regiment in the Apennine mountains where it was serving in an infantry role. As he was only 19 his father had had to sign a certificate to allow him to be posted overseas. Commanding a tank troop, he fought in the final phase of the Italian campaign with 6th Armoured Division which broke through the Argenta Gap and broke the German line in the plain of the Po. His unit was among the first into Austria where the British Army had to deal with a complex array of problems that would have taxed Solomon. As Austria became more settled, life for a soldier eased. These were heady times for a young soldier. Michael shot chamois on Hermann Göring's mountain estate in Austria and he kept the Mess in trout with regular forays to the Alpine streams and lakes; and cavalrymen were in their element here, with the pick of the liberated Austrian and German horse flesh at the allies' disposal. McCorkell was involved in two enormous tattoos at the Schönbrunn Palace in Vienna and at the Olympiastadion in Berlin, where he and others performed cavalry trick rides. He was a Major in the Territorial Army and North Irish Horse. His long involvement with the North Irish Horse, which he joined on the formation of the TA in Northern Ireland in 1947, had already seen him commanding it in the 1960s and, without hesitation, he became T & AVR Colonel, Northern Ireland, in 1971-1974, Aide-de-camp to Queen Elizabeth II, Aide-de-camp to Governor of Northern Ireland, Brevet Colonel, Honorary Colonel of the North Irish Horse in 1975 and President of the T & AVR, Northern Ireland in 1977.
In extreme secrecy, what is now believed to have been the first meeting between the Provisional Irish Republican Army and senior officials of the British Government took place at Ballyarnett, Colonel Sir Michael’s family home, 20 June 1972. The IRA was represented at that meeting by Dáithí Ó Conaill and Gerry Adams, and the British government was represented by Frank Steele, believed to be an MI6 agent, and Philip Woodfield. The meeting lasted four hours and the British side informed the IRA representatives that while Willie Whitelaw refused to offer political status, he was prepared to suspend arrests of republicans and searches of homes. Both sides then agreed to call a ten-day ceasefire. In September 2019, BBCNI's 'Spotlight On The Troubles', , covered these historic talks and visited Ballyarnett to film, which had by now been sold by the McCorkell family. The episode also included an interview with their son David McCorkell, who disclosed extracts from Lady McCorkell's private journal about the event for the very first time. Further extracts from the journal were later released by the media
