MW,
The requirement for a Sanhedrin and Navi only refers to milchemet reshut not a milchemet mitzva (Ramban, Hilchot Melachim 5:2; Ran, Derash 11; Netziv, He’emek Devar, Deavrim 17:14; Rav Kook, Mishpat Cohen 144)
Rav Herzog (Heichal Yitzchak OC 31 and 38), the Tzitz Eliezer (3:9:10, 3:10, 7:48:12) and Rav Ovadia (Yabia Omer 10 CM 6:23 on the Entebbe operation) say that Israel’s wars have been milchemot mitva.