This article references a new(old) piece by Leithart reviewing Yoder's view of the Old Testament: here
Leithart assesses Yoder's compiled writings on the Old Testament and finds it lacking. To summarize quickly, Yoder, a Mennonite, saw Christianity as non-violent, but was catholic enough in his spirit to abhor the Marcionite spirit one can find among modern Anabaptists. He views the OT as pedagogical, where God brings a people under His law, and begins to reshape and direct them. This direction is fundamentally angled towards non-violence and faith in God, the One who will fight Israel's battles.
Leithart finds this lacking, but is fundamentally mistaken. This is more apparent in how he right corrects Yoder (at least his reading) without appreciating the edge of what he seems to be saying. Yoder, says Leithart, doesn't rightly understand the pedagogical, "canonical direction", of Israel. Rather than seeing God assume more and more of Israel's violence, one sees this diffuse. There is a contrast between the God who breaks the back of Egypt's army through the waters, or miraculously empowers Israel's arms through Moses' lifted arms, and David, God's Anointed one, who leads Israel's armies in campaigns to secure the land. Instead, says Leithart, one should see, "Growing up might mean that the kids learn to fight alongside daddy [God], rather than watching him handle all the baddies."
Leithart properly understands this maturation process, but Judaizes the sword. He turns back the Sword of the Spirit the Church is given into one of bronze.
It is not clear how Leithart properly assesses how the reign of Christ is actually different than that of Israel. He cites Mordecai's gathering of a militia under the Persian emperor in Esther, but there's slippage. The book of Esther is in the period of Exile, but it is not in the age of Pentecost. This citation seems to belie an assumption that the Christian can serve under the magistrate for the purposes of military conflict.
The only relevant point is that Leithart recognizes that St. Paul speaks of the sword of the Spirit, and that "these all refer to "spiritual" warfare, but in the Bible the wars of the Spirit are also political events." This is a naked assertion without definition. What is a political event? What does that have to do with the machinery of the state? Where and what is a war of the Spirit in the Bible? Elijah versus the Prophets of Baal? The Apostle Paul calling blindness upon a false prophet? This is the fundamental weak-point in almost all pro-war statements for the New Testament. They all depend on post-facto reasoning. The only reason we assume that we ought to pick up our swords and guns is that is what ecclesiastical history tells us.
Leithart could theoretically back-peddle out of this justification for military-state violence, but then he'd completely miss what Yoder is trying to argue. Yoder's major concern was primarily Chrisitan complicity in violent conquest. This was the Anabaptist critique, which then radiated out to condemning all earthly political machinery and apparati. It is almost as if Leithart cannot understand Yoder, and can only offer surface critiques, missing the core argument. He cannot answer that fundamental question: How is the Sword of the Spirit not a sword of metal?
What happened on Pentecost that changed how the Christian Church ought to function with regards to coercive violence? In some ways, this is generally a failure by the Reformed, who generally cannot tell the differences between the before and after of Christ's Work, manifest in the faulty understanding of the Lord's Supper and Baptism. Leithart reflects this general ambiguity and embarrassment, not understanding what Christ means when He says His Kingdom is not of this world/age.
While I am not a Pacifist, at least in any consistent or doctrinaire sense, if one wants to rebut Yoder's project, one has to articulate what the radical breakage before and after the Advent of the Lord entails. The Spirit was active throughout the high times of Israel, empowering Samson to preach Death's death in the very temple of the Devil, or bringing a Gentile like Namaan to recognize the True God of Israel and worship Him. What has Christ accomplished?