Did any other church father other than St. Augustine believe in the just war theory?

Clement of Alexandria could be added to the list of early church leaders who worked with a just war philosophy. The Encyclopedia Britannica on an article on Clement of Alexandria notes (emphasis added):

In keeping with the logos–nomos (word–law, or, sometimes, gospel–law) theme that pervades his works, Clement alluded to the theory of the two cities, the city of heaven and the city of the earth. Like St. Augustine, the great theologian who utilized the same theme two centuries later in De civitate Dei (The City of God), Clement did not equate the city of heaven with the institutional church. According to Clement, the Christian was to live under the Logos as befitting a citizen of heaven and then, in an order of priorities, under the law (nomos) as a citizen of the earth. If a conflict should arise between God and Caesar (i.e., the state), the Christian was to appeal to the “higher law” of the Logos. At one point Clement advocated the theory of the just cause for open rebellion against a government that enslaves people against their will, as in the case of the Hebrews in Egypt. In this view he also anticipated Augustine’s theory of the just war, a theory that has been dominant in Western civilization since the early Middle Ages. He also struck at racism when it is considered a basis for slavery.

In light of the above, it is important to read Clement of Alexandria in light of how he appears to advocate a view that allows for pagan religions to flourish under a secular government. For example, Clement writes:

If a loud trumpet summons soldiers to war, shall not Christ with a strain of peace issued to the ends of the earth gather up his soldiers of peace? By his own blood and by his word he has assembled an army which sheds no blood in order to give them the Kingdom of Heaven. The trumpet of Christ is his Gospel. He has sounded it and we have heard it. Let us then put on the armor of peace. (Exhortations to the Heathens, 11)

The dominant view of the early church was that it was not a just war to fight against pagan religions and outlaw them in the Roman Empire. For example, Tertullian writes to the proconsul of Africa, Scapula:

It is only just and a privilege inherent in human nature that every person should be able to worship according to his own convictions; the religious practice of one person neither harms nor helps another. It is not part of religion to coerce religious practice, for it is by choice not coercion that we should be led to religion.

It is interesting how Nathaniel Peters writes in his article A Christian Case for Religious Liberty:

1814 Jefferson purchased a copy of Tertullian, now in the Library of Congress. When Wilken opened it to Ad Scapulam’s passage on religious liberty, he found a large X marked in the margin.

In another work Tertullian writes still more forcefully about the freedom of religion:

Let one man worship God, another Jupiter. … For see that you do not give a further ground for the charge of irreligion by taking away religious liberty and forbidding free choice of deity, so that I may no longer worship according to my inclination, but am compelled to worship against it. Not even a human being would care to have unwilling homage rendered him.

As a previous post by Dan Fefferman points out, the endors*m*nt of military action by Tertullian to keep the peace is implied in this quote:

Without ceasing, for all our emperors we offer prayer. We pray for life prolonged; for security to the empire; for protection to the imperial house; for brave armies, a faithful senate, a virtuous people, the world at rest, whatever, as man or Caesar, an emperor would wish. (Apology, 30:4)

Anticipating Tertullian, Justin Martyr writes:

We refrain from making war on our enemies...For Caesar's soldiers possess nothing which they can lose more precious than their life, while our love goes out to that enteral life which God will give us by His might. (Contra Celsum, v. 33; viii. 73)

Augustine was the first. To the extent that the early Fathers addressed the issue of war, they were opposed to Christian participation in it. A typical comment of this type is found in the writings of Clement of Alexandria, who said:

Above all Christians are not allowed to correct sinful wrongdoings by violence.

{note: see addendum for better examples}

Prior to Augustine the closest thing to an endors*m*nt of military action is found in Tertullian. Like Augustine in a later century, he lived in North Africa, where imperial armies were thought essential to keep the peace:

Without ceasing, for all our emperors we offer prayer. We pray for life prolonged; for security to the empire; for protection to the imperial house; for brave armies, a faithful senate, a virtuous people, the world at rest, whatever, as man or Caesar, an emperor would wish. (Apol. 30)

Things would change in the course of events when Christians became emperors. From St. Augustine in the West to St. Justinian in the East, theologians would come to see the use of the sword as acceptable in the defense of the true faith.

Addendum

Since my example from Clement has been rightly challenged I include here quotes from the same linked page which make the same point:

• "Only without the sword can the Christian wage war: the Lord has abolished the sword.” -- Tertullian
• "We ourselves were well conversant with war, murder and everything evil, but all of us throughout the whole wide earth have traded in our weapons of war." - Justin Martyr
• "Christians have changed their swords and their lances into instruments of peace, and they know not now how to fight.” - Irenaeus
• "Anyone taking or already baptized who wants to become a soldier shall be sent away, for he has despised God.” -- Hippolytus