He also played for several other Scottish clubs, in England with Bolton Wanderers, in Wales (albeit in the English Football League) with Cardiff City, and on both sides of the border in Ireland with Ballymena and Dundalk.
[7] Following the outbreak of World War I, Cassidy enlisted in the Black Watch (Royal Highlanders) 1/7th Fife Battalion, and was awarded the Military Medal in November 1918.
His eleven goals in a single Scottish Cup campaign remains a joint club record, Jimmy McGrory (his understudy and then successor in the squad) having equalled the tally in the 1924–25 season.
After two seasons with Dundee and one with Clyde,[7] in 1929 Cassidy moved to Ireland, joining Ballymena, helping the club to victory in the 1929 Irish Cup final, defeating Belfast Celtic 2–1.
[2] Due to his regular changes of clubs during the 1920s, Cassidy's first four children were all born in separate countries of the United Kingdom, Scotland, England, Wales and Northern Ireland.