War is a tool of God.
There are many unacceptable reasons for war. Imperialism. Financial gain. Religion. Family feuds. Racial arrogance. There are many unacceptable motives for war. But there is one time when war is condoned and used by God: wickedness. When calling the Israelites into battle. Moses carefully instructed them:
"After the Lord your God has done this for you, don't say to yourselves, 'The Lord has given us this land because we are so righteous!' No, it is because of the wickedness of the other nations that he is doing it." (Deut. 9:4)

Can people grow so wicked, so pagan, so vile that God justifiably destroys them? Can leaders be so evil and cruel that God, knowing the hardness of their hearts, righteously removes them from the earth? Apparently so. He did so with Sodom and Gomorrah. He did so with the Hittites, Amorites, Canaanites, Hivites and Jebusites.

"As for the towns of the nations the Lord your God is giving you as a special possession, destroy every living thing in them. You must completely destroy the Hittites, Amorites, Canaanites, Perizzites, Hivites, and Jebusites, just as the Lord your God has commanded you. This will keep the people of the land from teaching you their detestable customs in the worship of their gods, which would cause you to sin deeply against the Lord your God." (Deut. 20:16-18)

God has used warfare as a form of judgment against the enemies of God. In fact, He uses warfare as judgment against his own people when they become enemies of God.
"O Israel, I will bring a distant nation against you," says the Lord. "It is a mighty nation, an ancient nation, a people whose language you do not know, whose speech you cannot understand. Their weapons are deadly; their warriors are mighty. They will eat your harvests and your children's bread, your flocks of sheep and your herds of cattle. Yes, they will eat your grapes and figs. And they will destroy your fortified cities, which you think are so safe." (Jeremiah 5:15-17)

God's priority is the salvation of souls. When a people-group blockades his plan, does he not have the right to remove them? He is the God who knows "the end from the beginning" (Isa. 46:10). He knows the hearts of men and protects his people by punishing the evil of their wicked neighbors. Is it not God's right to punish evil? Is it not appropriate for the one who tells us to hate that which is evil to punish that which is evil? Of course it is.

And--this is crucial--he uses governments to do so.
"Obey the government, for God is the one who put it there. All governments have been placed in power by God... ...The authorities are sent by God to help you. But if you are doing something wrong, of course you should be afraid, for you will be punished. The authorities are established by God for that very purpose, to punish those who do wrong." (Romans 13:1,4)

Scripture elevates the role of government to a high place. Their position is a God-given assignment. Paul echoes this truth three times:
All governments have been placed in power by God.
The authorities are sent by God.
The authorities are established by God.
The noun Paul employs for "authorities" is diakonoi- the same word from which we translate deacon. Those in authority, the President, the soldiers, Secretary of Defense and so forth, are God's deacons and deaconesses--as ordained for their task as is any preacher or evangelist. Their role is clear: protect and punish. Protect the innocent and punish evil. When the government perceives that her people are under threat, when negotiations have proven fruitless and olive branches have gone unacknowledged, when the leaders of a country are convinced that an attack against evil will preserve that which is good and protect those who are innocent--then, and only then, war is justifiable.

Content provided by: Oneplace.com