Conflict = disagreement between two or more people. When conflict happens on a national or international scale, it's war.
Jewish Bible provides many examples of ancient Israelites engaging in armed conflict.
Sometimes, it's clear God supports battle.
Three kinds of war that are justified.
Obligatory wars – God has commanded. (Two are recorded in the Jewish Bible.)
Defensive wars – Fought in self-defence or to prevent being attacked.
Optional wars – These are Just Wars that fulfil certain conditions:
last resort
limit killing to combatants and avoid civilians
enemy should be treated humanely: ‘If your enemy is hungry, give him food to eat; if he is thirsty, give him water to drink.’ Proverbs 25:21
Judaism accepts war may be unavoidable in some circumstances, but ideally strive for peace: ‘In God’s eyes, the man stands high who makes peace between men…But he stands highest who establishes peace among the nations.’ (The Talmud)
There are a significant number of Jews who believe that the teachings of Judaism inspire non-violence.(Pacifism and conscientious objectors)