In the Old Testament, God appeared as a war-God -- He would encourage religious wars and genocide; He encouraged stoning; He encouraged several violent things.
In the New Testament, God appeared in human flesh as a peace-God -- He encouraged non-violence even to the extent of self-sacrifice.
Why is this? Why didn't God directly show and teach the Beatitudes and the Our Father and unconditional love as such?
Forgive me.. I'm just curious -- this is usually what atheists punch Orthodoxy with.
Actually, in the New Testament, God appeared very much as a war-God. But to paraphrase St. Paul, Christ's battle was not against flesh and blood, but against Satan and death. The Orthodox Church has always placed a heavy emphasis on Christ's Crucifixion and Resurrection, for example, as the glorious acts of a victorious warrior King, who vanquishes His foes and smashes their heads against the rocks. On the topic of self-sacrifice, the Desert Father's (and even Friedrich Nietzsche) agree that asceticism is warfare to the last breath.
Basically the battlefield has just moved from the outside to the inside. But our God is still the Lord of Hosts (armies)!
Think of the Paschal troparion itself: it's hard to "trample" someone peacefully! But of course, Jesus doesn't encourage His followers to take up the sword, but to take up their cross, as He did, because as he says to Pilate, His Kingdom is not of this world.