Complex sentence: The training German units provided to Nationalist forces would prove valuable; by the War's end, perhaps fifty-six thousand Nationalist soldiers encompassing infantry, artillery, aerial and naval forces had been trained by German detachments.
Split into simpler sentences: The training German units provided to Nationalist forces would prove valuable. By the War's end, perhaps 56,000 Nationalist soldiers, encompassing infantry, artillery, aerial and naval forces, had been trained by German detachments.