May 26

1722:

The Royal Artillery is formed. This day is observed in the Royal Regiment of Canadian Artillery as Artillery Day. (The origins of the RCA are too diverse for them to agree on one regimental birthday.)

1940:

Operation Dynamo begins; evacuation of 338,226 allied troops at Dunkirk

1944:

CEPRANO, effective dates for battle honour begin (to 27 May 44)