Suppose that one unit has an attack factor of 4 and health factor of 4. The other has a defense factor of 3 and a health factor of 2. When either has lost all of its health factor, he loses. The basic odds of winning are easy, 3 to 2 or 3/5= 0.6. The odds of losing 4 times in a row are easy: (1-0.6)^4 = 0.0256. The odds of the defender winning 2 times in a row are 0.4^2. But what are the odds that the defender will lose 2 times before the winner loses 4 times?