The Doctor is acutely aware of his own power. He is ruthless in the face of an invading army but only after offers of parley failed. He is willing to make life or death decisions when forced to yet he recognizes the cost to both the aggressor and himself. The Doctor has seen enough arrogance and greed to wither any heart yet he is determined to give the benefit of the doubt. Clara may be a soldier now but she does not have to be a conqueror. Soldiers are also protectors and explorers. They build as many bridges as they burn. Clara is not required to give up her humanity in order to become an effective leader. A general may not mourn in the moment of battle but that does not mean they never grieve for the consequences of war and their part in it.