Cruiser Tank” was the British term for its medium-weight tanks intended to be used by Armoured Divisions. The first was known as A9 after the original War Office specification for the type, A10 was very similar but had up to 30mm armour compared to 14mm. It was originally intended to be an Infantry Tank but instead became a “Heavy Cruiser” while the A9 became a “Light Cruiser”. When it was decided that even better-armoured tanks were needed, both were known simply as Cruisers. The naming system changed in mid-1940 after which A10 became Cruiser II. The change in armament from the Vickers machine gun to Besa was shown by the letter ‘a’ added to the designation, so they were designated A10 Mk Ia or Cruiser IIa.