rabbiofberlin, In any event, Milkhemes Mitzvah a war during the times of the Tanach when a king would go to war in order to fulfil something based on, and required by, the Torah without needing approval from a Sanhedrin, such as war against Amalek.
Milkhemes Mitzvah by definition is not applicable byom hazeh.
1. Rambam Hilchos Melachim 5:1,2