Complex sentence: By the end of 1942 most of the men had left the mine to join the army with the work force declining to 60, in June 1944 the mine closed at which stage the main shaft had reached 500 feet.
Split into simpler sentences: By the end of 1942 most of the men had left the mine to join the army with the work force declining to 60. In June 1944 the mine closed at which stage the main shaft had reached 500 feet.