Who said "One must study the enemy to defeat them effectively."?

This quote is attributed to Che Guevara.

One must study the enemy to defeat them effectively. - Che Guevara

"One must study the enemy to defeat them effectively."

Che Guevara

Revolutionary, Guerrilla Leader Argentine-Cuban 1928–1967

"The true revolutionary is guided by a great feeling of love. It is impossible to think of a genuine revolutionary lacking this quality."

"At the risk of seeming ridiculous, let me say that the true revolutionary is guided by a great feeling of love."

"Hasta la victoria siempre (Until victory always)."

"One person with a gun can control 100 without one."