The Parable of the Old Man and The Young by Wilfred Owen - Explanation

 The poem was written by Wilfred Owen, a distinguished poet and foremost, a soldier of the first world war. 

The poem alludes to a biblical "parable", which refers to a short religious/morality-based story.

The biblical character of Abraham climbs to Mount Moriah along with his son, Isaac. It is the command of the Almighty that Abraham shall offer his firstborn, i.e. Isaac as a sacrifice at Mount Moriah. Abraham doesn't flinch at this unusual and pitiless command, but as he begins to undertake this act, an Angel appears and points to a ram and says that it could be offered as a sacrificial gift in place of his son, and thus Isaac's life is saved.

Owen amended the parable and compares it to mass death and destruction due to the erstwhile first world war (1914-19).

The poem begins with Abraham and Isaac approaching near their destination, Mount Isaac. Abraham carries a knife and a fire with him.

Isaac is done with the preparation of the sacrifice and his asks his father with wonder whether he has the supposed lamb to offer to God. Then Abraham "bound the youth with belts and straps", this line suggests two meanings, its literal meaning is that Abraham ties Isaac because he is the human sacrifice and the latter is unaware about it.

Owen alludes to the ongoing war that had wreak havoc in Europe. He also insinuates that rulers and politicians wage war on each other due to vested interests. They either order recruitment of young, naive men forcefully or with jingoistic statements and make them wear "belts and straps" and push them to the battlefield where they fight taking cover in trenches and parapet.

Coming back to our parable, Abraham holds his knife and as he tries to stab his son, an Angel appears and asks him not to kill his son. He points to a ram ("Ram of pride" means the sin of pride) caught in a bushes with its horns and tells him to offer it instead of Isaac.

But the old man refuses to listen to his advice and stabs his own son. By not recognizing and renouncing his pride, Abraham took the ruthless and inhumane step of killing his own son. 

In the same way, rulers, like Abraham, wage war to score brownie points. Due to their vanity and unbridled power, countless innocent lives are lost in the war.