Erich von Manstein was a field marshall in WWII. He was one of the commanders the Allies feared the most. He was one of the Wehrmacht's best military strategists. After the war he was sentenced to 18 years in prison but ultimately only served four and went on to become a military advisor to the West German government.
They used to call it the art of warfare. War as a game of strategy. Certain moves can be considered brilliant, like the French campaign, his greatest triumph. Some moves required brute force, such as the conquest of Crimea and Sevastopol, the world's strongest fortress.
"My most able general", said Hitler, "is the most dangerous opponent" said the allies. A Prussian field marshal obsessed with duty, discernment, and obedience.
Why wage war for a criminal? Why obedience to the very end? There is virtually no other commander-in-chief who fought as many battles with Hitler and contributed as much to solutions at the front as Manstein did.