The term "justice and peace" did not exist in the time of Augustine.
Even so, he saw the correlation of justice and peace as necessary if a society was to be truly Christian. Justice, as Augustine understands it, requires right relationships, including a more perfect distribution of the goods of the world in order to reflect more clearly the love of God for all of creation.
A person is "just when he seeks to use things only for the end for which God appointed them, and to enjoy God as the end of all, while he enjoys himself and his friend in God and for God." (City of God 15.22). Our relationship with God urges us to see one another in a different fashion. We belong to one another and are responsible for one another.
To Augustine, human beings are called to go beyond indifference and even discrimination in order to establish a more full communion, in the image and likeness of the God. Peace, for Augustine, results when the parties concerned agree to work with and not against each other. All human beings seek peace, Augustine reminds us, but we only rarely seek true justice.
True justice - that is, right relationships - demands of us to be aware of and involved in rectifying the present international situation which sees 24,000 people dying of hunger each day. A "just" war seeks a "just" settlement: a redistribution of the goods of the world that would allow all to eat and nourish themselves.