Short answers, pulled from the story.
Carl von Clausewitz is best known for his treatise Vom Kriege, published in English as On War, which is considered a seminal work on the philosophy of military strategy. He is also famous for the aphorism "War is the continuation of policy with other means" and for the concepts of the fog of war and friction in military thinking.
Carl von Clausewitz was born on the 1st of July 1780 in Burg bei Magdeburg in the Prussian Duchy of Magdeburg. He died on the 16th of November 1831 of cholera while serving as commander of Prussian forces on the Polish border.
On War was not finished at Clausewitz's death. He had started working on the text in 1816 and was actively revising it between 1827 and his departure on his last field assignments. His widow, Countess Marie von Clausewitz, edited, published, and wrote the introduction to the work in 1832, and had published most of his collected works by 1835.
Clausewitz's trinity, which he called the wunderliche Dreifaltigkeit or "fascinating trinity," describes war as a dynamic and inherently unstable interaction of three forces: violent emotion, chance, and rational calculation. It is frequently but incorrectly reduced to "people, army, and government," a misrepresentation popularised by U.S. Army Colonel Harry Summers in his Vietnam-era interpretation.
Vladimir Lenin called Clausewitz "one of the great military writers," and the American mathematician Anatol Rapoport argued in 1968 that Clausewitz as interpreted by Lenin formed the basis of all Soviet military thinking since 1917. Mao Zedong read On War in 1938 and organised a seminar on Clausewitz for the Communist Party leadership in Yan'an, making his engagement with the text direct rather than filtered through Lenin.
The phrase "fog of war" derives from Clausewitz's stress on how confused warfare can seem to those immersed within it, given incomplete, dubious, and often erroneous information, combined with great fear, doubt, and excitement. Clausewitz was deeply skeptical of military intelligence at the tactical and operational levels, writing in On War that "most intelligence is false."