Gustavus Adolphus the Great

[Alexanderofmacedon]

The thirty years war was absolutely insane.

I believe it was Maurya after his "conquest" of King Porus.

[Oleander Ardens]

Gustavus adopted many tactical and technical innovations from abroad, especially from the Dutch. Small linear infantry formations, extensive drills for rapid fire and many other aspects of his army were already well known at his time. However as a King he was able to marshal the ressources of his land into building a solid army with excellent training and equipment, fine discipline and great tactical skill. Good logistics and regular pay kept his men marching.

So he had time and ressources to build an army into a mighty tool wielded by his great skill as commander. I think his successes were due to this synergies of state and army, tactical innovations and strategic skill.