Complex sentence: Two 4th Fighter Regiment machines were tasked with escorting Bristol Blenheim Mk I light bombers to attack targets in Austria, but they lost their charges in cloud, after which one of the pilots attempted to intercept some German Messerschmitt Bf 109 fighters.
Split into simpler sentences: Two 4th Fighter Regiment machines were tasked with escorting Bristol Blenheim Mk I light bombers to attack targets in Austria, but they lost sight of the bombers in cloud cover. One of the pilots then attempted to intercept some German Messerschmitt Bf 109 fighters.