Augustine believes that the condition of war arises when the perfectly ordered and harmonious enjoyment of God is disrupted (The City of God, 690) whereas Hobbes believes that the original state of nature is a condition of constant war, which rational and self-motivated people want to end.
Augustine argues that peace is more than the absence of hostilities - it is a state of harmony that makes possible the full functioning of human beings. Full functioning comes from the four internal virtues (courage, justice, temperance, and prudence) that we must exercise to achieve good human morality. Human morality, by and of its self, will not allow us humans to travel to our moral destination. It is only an exercise of the four virtues so that we as humans can achieve some sort of peace on our own through God's saving grace.
To Augustine, humans seek an object of love they can't lose. The problem with that to humans is that humans can't provide that to other humans completely. Only God can and that in turn causes hostility among humans. The love of God, then, is the only way humans can completely satisfy all four virtues and have eternal peace. Eternal peace is where faith, love, and hope are to be enjoyed, such as in The City of God.
In Book XIX, Augustinian social theory summarizes the principle of ordered harmony. This theory finds perfection in a mutual society that believes in God. Believing in God, though, lends a problem in the simple rule of justice: how do we give each other their due? Seemingly, war or hostility would not be a part of a Christian's life on earth. Augustine counters by indicating that war may be and is waged by God's commandment. To Augustine, waging war out of obedience to God is very different than to wage war for personal gain. But even wars caused by unselfish humans...