who during WWII made efforts to help Jews escape the holocaust, and who as pope (Oct. 1958-Nov. 1963) took steps to improve relations between Catholics and Jews. From wiki:
One of the first acts of Pope John was to eliminate the description of the Jews as "perfidious" in the Good Friday liturgy. He also made a confession for the Church of the sin of anti-semitism through the centuries. http://en.wikipedia.org/wiki/Pope_John_XXIII
Three months after his election in 1958, he announced plans to conven an Ecumenical Council, the first in 90 years, for the purpose of improving relations with other religions, and in Oct. 1962, he launched the storied Second Vatican Council for the purpose of modernizing the Church.
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Mosaic image of Pope John XXIII the Basilica of Saint Paul Outside the Walls Rome
John died on June 3, 1963, six months before JFK's assassination. Vatican II finished up in Dec. 1965, and made a lot of waves which are still crashing on the heads of refuseniks like Mel Gibson and his father who never let go the Latin liturgy. It did away with other practices too, like fasting on Fridays and guardian angels, and adjusted Catholic relations with the world, abandoning scary stuff like black burqua-like habits for nuns and replacing it with more humane, less parochial approaches. His eighth and final encyclical,
Pacem in Terris, "Peace on Earth," published April 11, 1963, is dedicated to "establishing universal peace in truth, justice, charity, and liberty," translation here:
http://saints.sqpn.com/pope-john-xxiii-pacem-in-terris-peace-on-earth-11-april-1963/
Among other accomplishments John kicked off his papacy with a Christmas mass in an Italian prison:
On 25 December 1958, he became the first pope since 1870 to make pastoral visits in his Diocese of Rome, when he visited children infected with polio at the Bambino Gesù Hospital and then visited Santo Spirito Hospital. The following day he visited Rome's Regina Coeli prison, where he told the inmates: "You could not come to me, so I came to you." These acts created a sensation. . . . http://www.newworldencyclopedia.org/entry/John_XXIII
Here's a good vid (short too, only 52 seconds!) on the 4-1/2 year reign of John XXIII, still beloved by many but probably hated by more: