The army increased its effectiveness and success rate through a series of trials and errors, often at great human cost. General Washington and other distinguished officers were instrumental leaders in preserving unity, learning and adapting, and ensuring discipline throughout the eight years of war. In the winter of 1777–1778, with the addition of Baron von Steuben, a Prussian expert, the training and discipline of the Continental Army was dramatically upgraded to modern European standards. (This was the infamous winter at Valley Forge.) Washington always viewed the Army as a temporary measure and strove to maintain civilian control of the military, as did the Continental Congress, though there were minor disagreements about how this was to be carried out.