Complex sentence: The three cavalry regiments mechanised slowly during 1940 but only on the Motor regiment establishment, being mounted in soft skinned trucks, eventually with some 2-pounder anti-guns but still chronically ill-equipped, especially of radio, when they went into action in April 1941.
Split into simpler sentences: The three cavalry regiments mechanised slowly during 1940 but on the Motor regiment establishment, not armoured. This meant they were mounted in soft skinned trucks, eventually with some 2-pounder anti-guns but were still chronically ill-equipped, especially of radio, when they went into action in April 1941.