Unlike the 1914-18 period, rugby continued to be played throughout the war years 1939-45. There was however a curtailment of activity due to fuel shortages, etc. The club’s Golden Jubilee was celebrated in 1941-42 when J.Watson was President. Many of the men who had founded the club were on hand to celebrate the occasion on January 17th 1942 at the Metropole Hotel.

Ned O’Connor captained his team to success in the Munster Senior Cup in 1942 when they defeated UCC 9-3 in the final. The Cup was retained the following year when the Constitution three-quarter line was deemed to be the best of all time, and were nicknamed the ‘million dollar back line’. The captain, Cecil O’Driscoll was a much admired player who was unfortunate not to be capped, as was out half, Tommy Moroney. They scored five tries against a strong Irish Army XV winning 22-0 at Thomond Park, which had become the Branch venue in Limerick.

John Irwin was captain in 1946 when Constitution defeated Garryowen in the Munster Senior Cup final in front of a capacity crowd at the Mardyke. The game was scoreless coming to the final minutes when Moroney broke on the blind-side to release wing Tom Riordan. He had it all to do against a formidable Garryowen defence but made it to the corner to the joy of the Constitution supporters.

J.C.Daly from Cobh, who served with the Allied armies in the war, had joined Constitution and was a key player in the 1946 Cup triumph. He was selected for Ireland in the 1947 & 1948 Five Nations games and scored the winning try at Ravenhill against Wales in 1949 to secure the Triple Crown and Grand Slam, after which he was shouldered from the field by supporters who also took his jersey as a souvenir.

There was another final defeat by Richmond in 1946 before the elusive Munster Junior Cup was finally captured. After nine previous final defeats, St Mary’s were beaten 11-0 at the Mardyke in 1949. Peter Fitzgerald was the joyous first captain to lift the Cup.

The touring Wallabies played Munster at the Mardyke in December 1947 in a memorable match. Batt Hayes and Jack Mackesy were on the team that lost 5-6.

Dan O’Connell and Noel Murphy served as Presidents Munster Branch IRFU during the period.

Officers	Competitions
Season President Captain 1940-41 E.Gayer W.A.Nestor 1941-42 J.H.Watson E.O'Connor 1942-43 J.Riordan C.J.O'Driscoll 1943-44 P.J.Delaney C.Crowley 1944-45 J.J.Horgan T.Riordan 1945-46 J.R.Cunningham J.Irwin 1946-47 T.M.Casey J.Costigan 1947-48 J.V.Rearden J.Mackesy 1948-49 N.F.Murphy N.Nunan 1949-50 J.Tierney D.Crowley   Season President Munster Branch 1942-43 D.F.O’Connell 1949-50 N.F.Murphy	Munster Senior Cup 1941-42 1942-43 1945-46     Munster Senior League 1944-45   Cork Charity Cup 1942-43 1943-44 1944-45