Complex sentence: The General Staff was aware that the Crusader would become obsolete, and in late 1940 they set out the specifications for the new replacement tank, to be fitted with the QF 6 pounder gun and was expected to enter service in 1942.
Split into simpler sentences: The General Staff was aware that the Crusader would become obsolete, and in late 1940 they set out the specifications for the new tank to replace it. The tank was to be fitted with the QF 6 pounder gun and was expected to enter service in 1942.