Prior to the outbreak of WWII, Britain relied heavily on military alliance with France. It was felt that the large French army would be able to check any German expansion in western Europe should existing treaties be violated. As a result the British Army had been neglected, so that when war came the Royal Armoured Corps had only a handful of modern tanks in service. Many of these were sent to France with the BEF only days before France was defeated, all were abaondoned as their cres were evacuated back to Britain. The result was that new tanks were rushed into production without proper testing and were to prove unreliable in combat. As no new tank engines had been developed, most of these tanks were powered by the Nuffield Liberty, an American engine designed in WWI to give an output of 200bhp. Nuffield increased the output to 350 – 410 bhp and this was used to power the A13, A15 Crusader and A24 Cavalier. The engine proved adequate in the A13 and Crusader due to their modest weight, but in the Cavalier it was a disaster and the tank was unfit for combat. In 1941 Rolls Royce produced a de-rated version of their Merline aero engine, used in the Spitfire, Hurricane, and Lancaster aircraft, for tank use. Named the Meteor, this engine developed 600 bhp, more than enough for current needs.