Saying later that "those were the times" does not exonerate you from the sins committed.
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This is a good example of choices that we might face in our lives.
We all have a choice not to participate in the insanity (or "immorality") of war. In fact, if we all did, wars wouldn't exist at all.
Refusing to go to the battlefield and kill other young people is not immoral. It is the most moral and humane thing you can do.
If you ever need to make that choice, remember this.
I highly recommend reading Tolstoy's "The kingdom of God is within you", were he does a very deep analysis of war, state, violence and Christianity not as religion, but as a non-violent philosophy of life.