Maybe someone remember seeing this movie too... I was just a kid then
I remember this mighty warrior, invincible like, that no other warrior can match.
He has to leave his wife to go off to war.. she's having a baby\son but doesn't tell her Viking-like husband.
He leaves his wife his ring, I think, maybe a medallion.
She's captured by the enemy. She give the ring to her very young son. He wears it on a chain around his neck.
She dies.
The son grows up very strong and powerful like his father.
The enemy king trains this young warrior, so he can send him out to defeat his real father.
There's an EPIC battle of rival armies... everyone's killed but these 2 warriors.. as they fight the father see's his ring\medallion around the other warrior's neck, the son he never knew.

It must have been the early '60s when I last saw this.. haven't seen it since.

Ilya Muromets, It is a Russian film. The us version is called The Sword and the Dragon