"But there is one commandment (actually there are several) which you have to follow even if following it presents a risk to life and that is the milchemet mitzvah."
(Havn't listined to Chaim's answer yett), but I think it isn't just straight out like that. Meaning that if this would be the case, then Jews would have to keep fighting no matter what the consequences would be, even death for most or all of them (G-d forbid). It is different then the 3 that a Jew no matter what should give his/her own life up for. (Murder, having illicit relations, worshiping other gods).
With this case its more complex, but I believe that on the personal level, yes one would possibly have to give up his life as a soldier, but as a society and as an army it is more complex, becuase it should not only and always be to attach for the sake of the Mitzva. Sometimes during a battle if one needs to retreat then what can you do, you have to do that. And other times the best stratigic solution is to keep going foward. It all depends on what either a prophet says, or for today a good general (but one who in actuality wants to win, and wants to and does seek the benefit of the nation). Even King David Alav Hashalom had some retreats and defeats, but in the long run, he captured a lot of new land, becuase he knew what he was doing and G-d was with him.
בס''ד
Unfortunately, Tzvi again presents us with the defeatist mentality of the Charedim that he so admires.
There is nothing complex about milchemet mitzvah (an obligatory war). When there is an obligatory war, Jews are
required to fight and be willing to give their lives if necessary. The three things that Jews must be willing to die for (murder, sexual immorality and idolatry) are for Jews as
individuals. But when Jews are called upon to fight on a
national level, they must be willing to die if necessary to protect their nation, their land and their people, and for kiddush haShem (sanctifying G-d's name). If we instructed Jewish soldiers with the cowardly defeatism of most of the Charedim, we would face an immediate holocaust G-d forbid.
Avraham avinu, David HaMelech, Yonatan, Moshe Rabeinu, Yehoshua bin Nun and the other great leaders of the Tanach all fought with incredible bravery
against all odds and commanded soldiers who did the same. None of them ever displayed the gutless ghetto mentality of the Charedim.
We saw during the holocaust how the Charedim overwhelmingly did
not fight back. They went to the gas chambers and the ovens with little or no resistance. And they allowed the German Nazis ysv"z sr"y to murder their wives and children and parents and grandparents. This is
not the Jewish way! This is
not what the leaders of the Tanach would have done. This was one of the most shameful periods of Jewish history, and it was a huge chillul hashem (desecration of G-d's name).
Today, these same Charedim have learned
nothing from the horrors of the holocaust. They overwhelmingly did not serve in the Israeli army, and their leaders support cowardly retreats from the Land of Israel in exchange for government money (bribery) for their institutions. This is also
not the Jewish way!