401 Squadron, he achieved a number of aerial victories and was awarded the Distinguished Flying Cross (DFC) before going to a staff posting with No.

Educated at St. Michael's College School, he joined the Royal Canadian Air Force (RCAF) in June 1941, shortly before he turned 19 and was allocated the service number J/12199.

It began to train in ground support operations; having received Spitfire Mk IXs in October, was increasingly engaged in what were known as Ramrod and Rodeo missions; bomber escort and fighter sweeps respectively.

On 28 June Klersy destroyed a pair of Fw 190s east of Domfront and while flying in the area around Caen, he shot down a Messerschmitt Bf 109 fighter on 2 July.

He engaged and damaged a FW 190 on 13 July and four days later shot down a Dornier Do 217 medium bomber north of Caen.

[2] The official announcement was made in early September 1944 and the citation, published in The London Gazette, read This officer has displayed the greatest keenness for operations.

He has completed a large number of sorties and his successes include the destruction of 7 enemy aircraft and many mechanical vehicles.

His example of determination and devotion to duty has been of a high order.In early January 1945, Klersy returned to operations with a posting back to No.

Poor weather inhibited operations but on 23 January, Klersy encountered and damaged an Arado Ar 234 jet bomber near Osnabrück.

On 19 April, with the Allied advance into Germany well underway, Klersy shot down a Fw 190 he intercepted while on patrol over Hagenow.

[2][12] Two days, leading the squadron in a patrol over northern Germany, several aircraft were spotted on a grass airstrip at Schonberg.

[2][4] A month after his death, it was announced that he was awarded the Distinguished Service Order in "recognition of gallantry and devotion to duty in the execution of air operations".

[14] Buried at the Groesbeek Canadian War Cemetery in The Netherlands, Klersy is credited with having shot down fifteen German aircraft, one of which shared with another pilot.