Uhm... Vartan was a general of the Byzantine Empire; it was due to internal troubles and to quell the Ostrogoths and the Bulgars (especially) that the Byzantines did not send troops to aid the Armenians. That aside, it was 66,000 Armenians against 300,000 Persians, though the numbers are almost surely inflated; more likely, maybe 15-20,000 Armenians against maybe four or five times that number. The point is, however, that the Armenians were not simply a peasant army, holding their pitchforks against trained troops. The Armenian forces were small in number, but well trained, well disciplined, and well equipped; the Persians relied on conscript troops; usually a whipmaster driving four or five naked or rag-covered young men carrying a long, pointy stick. The Avarayr plain was by the river; the Armenian positions were entrenched on the opposite side, forcing the Persians to attempt to fjord the water against hostile forces. It was only when Vassak Syuuni showed the Persian Immortal cavalry a hidden shallows that the Persians were able to flank the Armenian position and smash it. And even despite the tactical loss, it WAS a strategic victory; the Persian army, one of the strongest in the world, had its nose bloodied by a small army for a cause that would only ensure a heavy price of gold and blood. Before the battle, the Persians were adamant on converting the Armenians; afterwards, especially after the years-long guerrilla war waged by Vartan's nephew, Vahan Mamikonian, the Persians made an unheard-of peace with the Armenians, even appointing Vahan as the Marzban and giving Armenia autonomy. I guess you could say that the Persians "won the battle, but lost the war."