"Stop! I am asking you with all my heart. Stop!" Pope Francis cried in an address to the pilgrims in St Peter's Square on Sunday.
The 28th of July this year marks 100 years since World War I broke, a day the Pope labelled as "a day of mourning."
"All is lost with war, but nothing is lost with peace," he said.
The Pope highlighted the impact of the war upon children, who have the hope for a "decent life" taken away from them.
"Dead children, injured children, maimed children, orphaned children, children who have war relics for toys, children who do not know how to smile..."
The Holy Father also called for prayer for the "peoples and authorities" of the three war zones: Iraq, Israel and Gaza, and Ukraine.
"Join me in prayer that the Lord may grant [them] the wisdom and strength needed to push ahead on the path of peace, addressing every diatribe with the tenacity of dialogue and negotiation and the power of reconciliation," he said.
In commemoration of World War I, the Pope said, "As we remember this tragic event, I hope the mistakes of the past will not be repeated."
Source: Asia News