Complex sentence: The German High Command predicted they would need 200,000 men per month to make good the losses suffered, returning convalescents could supply 70,000--80,000 per month but there were only 300,000 recruits available from the next annual class of eighteen-year-olds.
Split into simpler sentences: The German High Command predicted they would need 200,000 men per month to make good the losses suffered. Returning convalescents could supply 70,000--80,000 per month but there were only 300,000 recruits available from the next annual class of eighteen-year-olds.