War is the province of chance. In no other sphere of human activity must such a margin be left for this intruder. It increases the uncertainty of every circumstance and deranges the course of events.
Source: War, Politics and Power, 1962.
-- Karl von Clausewitz, (Jun 1 1780-1831), Prussian military leader, author; His writings and book On War, expounded the philosophy of war and had enormous effect on military strategy, tactics in World Wars.