Irish rugby was to be affected badly not just by the two World Wars during the first half of the last century but also by the Easter Rising of 1916 in Ireland. Many of the club's members were among the soldiers of the Irish Regiments that lost their lives in the 1914-18 war.
Like so many other clubs, London Irish drifted into the early 1920s. It was not until 1923 when the Irish Free State was established and peace returned that the club was able to welcome players from across the Irish Sea on a regular basis. For London Irish it was like starting all over again.
By the late 1920s the club boasted its first "home grown" Ireland international in a mighty forward, S J 'Cags' Cagney who won 13 caps in the green jersey between 1925 and 1929. This decade saw the inauguration of regular fixtures against great clubs such as Leicester and Cardiff. Cagney was captain of the club in the 1928/29 season when it did the double over the other two London exiles clubs for the first time.
Another link with Leicester at this time was the created by Cecil Beamish, a son of the famous Cork-based brewing family, who played for the Midlands club before transferring to London Irish in the early 1930s. Cecil's older brother George also joined London Irish in 1930. He was a big man not just in stature but also in personality. He was to become captain of Ireland in 1932 and was to go on to become a famous Battle of Britain pilot in the Second World War.
Few matches were played during the war between 1940 and 1945. Many London Irish players found themselves in services' teams in far distant places. Nine of the players that played for the club in the 1938/39 season lost their lives and others never returned to England.