In reading about Operation Mars, I tend to see two relatively conflicting analyses of it. One would indicate that the offensive was a narrow failure, albeit a very bloody narrow failure, where the Soviet Western and Kalinin Fronts came within a whisker of winning but the USSR reinforced failure more than it should have, and the other is that Operation Mars was simply put an instance of Walter Model entirely outgeneraling his opponents to a point where Operation Mars was never going to do anything but fail (the third POV, that it was just a diversion, can safely be dismissed). So, the challenge, should you choose to accept it, is to find a way that Operation Mars does break through Army Group Center, as well as realistic results of any such breakthrough. In other words, if the Soviets do win, would their casualties actually prevent them from doing more than recapturing Rzhev or would this lead to a further set of offensives in Belarus that actually do more than add to the death toll?