YES THERE IS MILCHEMET MITZVAH IN OUR TIMES!
The Ramban writes, “Behold we were commanded with conquest in every generation.” (Supplement to the Rambam, Sefer HaMitzvot, positive commandment #4).
The Rambam give 3 definitions of Milchemet mitzvah and the 3rd, “To save Israel from the hand of the enemy.”(Rambam, Mishneh Torah, Hilchot Milachim, 5:1)
So we have a milchemet mitzvah twice over, conquering the land and saving the nation.
Everyone must serve, yeshiva bachur or not!