Whether a person who has just built a new house is exempt from a non-Mitzvah war, if the house is less than 4*4 cubits: Succah 3a-b
For Torah Scholars to cease learning Torah for a war: Nedarim 32a; Sotah 10a How many judges are needed to send the nation out to a war which is not for a Mitzvah: Sanhedrin 2a
Removing a general from a City of Refuge to lead the nation in war: Makkot 11b King Asa was punished for conscripting the scholars: Sotah 10a
Going to War
Questioning the "Urim veTummim" before going to war: Eruvin 45a
Going to war on Shabbat to defend against invaders who seek to kill: Eruvin 45a
Going to war on Shabbat to defend against invaders who seek to plunder: Eruvin 45a
Defending a border city on Shabbat: Eruvin 45a
Other
Rain is a blessing in that it halts wars: Taanit 8b
