Clausewitz - "On War"

One of my long term books I've began reading is "On War". The first 68 pages consist of several forwards and introductions. It's heavy but good (I'm on page 19). I'm not a big quote person but my first favorite quote so far:

The conduct of war resembles the workings of an intricate machine with tremendous friction, so that combinations which are easily planned on paper can be executed only with great effort. Consequently the commander's free will and intelligence find themselves hampered at every turn, and remarkable strength of mind and spirit are needed to overcome this resistance. Even then many good ideas are destroyed by friction, and we must carry out more simply and modestly what in more complicated form would have given greater results