Avura, according to Ramban, conquering EY is a Torah mitzva. Rambam. Even according to those who only look at security, we cannot give up land. Look at what happened when we gave up Gush Katif. Obviously, war overrides pikuach nefesh of individuals.
So far as the O.P.’s question is concerned, there are a number of rabbis who alternated between the Mir and YU. I would imagine that the same is true of other Lithuanian yeshivot. Orthodoxy is represented by, to borrow a mathematical term, a continuous distribution, not a discreet distribution.