The Papal mediation in the Beagle conflict followed the failure of negotiations between Chile and Argentina, when, on 22 December 1978, the Argentinian Junta started Operation Soberanía, to invade Cape Horn and islands awarded to Chile by the Beagle Channel Arbitration. Soon after the event, Pope John Paul II, offered to mediate and sent his personal envoy Cardinal Antonio Samoré to Buenos Aires. Argentina, in acceptance of the authority of the Pope over the overwhelmingly Catholic Argentine population, called off the military operation and accepted the mediation. On 9 January 1979 Chile and Argentina signed the Act of Montevideo formally requesting mediation by the Vatican and renouncing the use of force.
The mediator acted to defuse the situation by negotiating an agreement that stopped the immediate military crisis. Then, the Vatican crafted a six-year process that allowed the parties to grapple with increasingly difficult issues, including navigation rights, sovereignty over other islands in the Fuegian Archipelago, delimitation of the Straits of Magellan, and maritime boundaries south to Cape Horn and beyond.
The 1978 military mobilization revealed other latent international relations issues between the two countries that had been previously overlooked or ignored.
By the beginning of November 1978, Chile and Argentina no longer had any mechanism for working toward a peaceful settlement and the situation began to destabilize rapidly. It was at this point, with direct talks dead and a judicial settlement refused by Argentina, that Chile suggested mediation. Argentina accepted the proposal and the two foreign ministers agreed to meet in Buenos Aires on December 12 for the purpose of selecting a mediator and the terms of mediation. Possible candidates were