"Never war! Never war! I think most of all about children, whose hopes for a dignified life, a future are dashed, dead children, wounded children, mutilated children, orphans, children who have the leftovers of war for toys, children who don't know how to smile. Stop it, please! I beg you with all my heart! It's time to stop!"

The Pope made his appeal after praying the noon Angelus with people gathered in St. Peter's Square July 27.

The Pope's plea came as he recalled the 100th anniversary of the start of the First World War, which, with more than 37 million causalities, was one of the deadliest conflicts in history. Beginning July 28, 1914, the "Great War" left "millions of victims and immense destruction," Pope Francis said.

The reigning pontiff at the time, Pope Benedict XV called it a "useless massacre," which ended after four years in a fragile peace, Pope Francis said.

He said July 28 would be "a day of mourning" and a chance for people to remember the lessons of history.

"I hope people will not repeat the mistakes of the past," he said, and will uphold "the rationale of peace through patient and courageous dialogue."

Highlighting the crises in the Middle East, Iraq and Ukraine, the Pope called for continued prayers so that the leaders and the people there would have the wisdom and will needed to choose peace with determination and face problems with "the tenacity of dialogue and negotiations."

"Let's remember that everything is lost with war and nothing is lost with peace," he said.

He urged that all decisions be based on respect for others and the common good — not personal interests.