Question: Operation Soberanía was a military invasion that began due to a border dispute between what two countries?
Context: 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 Croatia–Serbia border dispute refers to differing views held by Croatia and Serbia regarding their border in the area of the Danube River.  While Serbia holds the opinion that the thalweg of the Danube valley and the centerline of the river represents the international border between the two countries, Croatia disagrees and claims that the international border lies along the boundaries of the cadastral municipalities located along the river—departing from the course at several points along a 140 km section.  The cadastre-based boundary reflects the course of the Danube which existed in the 19th century, before meandering and hydraulic engineering works altered its course.  The area size of the territory in dispute is reported variously, up to 140 km2 . Operación Soberanía (Operation Sovereignty) was a planned Argentine military invasion of Chile started on 22 December 1978 due to the Beagle conflict dispute.  The invasion was halted after a few hours and Argentine forces retreated from the conflict zone without a fight.  Whether the Argentine infantry actually crossed the border into Chile has not been established.  Argentine sources insist that they crossed the border. Barbados v. Trinidad and Tobago was a 2006 arbitral case between Barbados and Trinidad and Tobago in which the tribunal resolved the maritime border dispute between the two countries.  The dispute was arbitrated before an arbitral tribunal constituted under Annex VII of the United Nations Convention on the Law of the Sea, in which the Permanent Court of Arbitration served as registry. Christ the Redeemer of the Andes (Spanish: "Cristo Redentor de los Andes" ) is a monument high in the Andes at 3,832 metres (12,572 ft) above mean sea level on the border between Argentina and Chile.  It was unveiled on 13 March 1904 as a celebration of the peaceful resolution of the border dispute between the two countries. The Adams–Onís Treaty of 1819, also known as the Transcontinental Treaty, the Florida Purchase Treaty, or the Florida Treaty, was a treaty between the United States and Spain in 1819 that ceded Florida to the U.S. and defined the boundary between the U.S. and New Spain.  It settled a standing border dispute between the two countries and was considered a triumph of American diplomacy.  It came in the midst of increasing tensions related to Spain's territorial boundaries in North America against the United States and Great Britain in the aftermath of the American Revolution; and also during the Latin American Wars of Independence.  Florida had become a burden to Spain, which could not afford to send settlers or garrisons.  Madrid decided to cede the territory to the United States through the Adams–Onís Treaty in exchange for settling the boundary dispute along the Sabine River in Spanish Texas.  The treaty established the boundary of U.S. territory and claims through the Rocky Mountains and west to the Pacific Ocean, in exchange for the U.S. paying residents' claims against the Spanish government up to a total of $5,000,000 and relinquishing the US claims on parts of Spanish Texas west of the Sabine River and other Spanish areas, under the terms of the Louisiana Purchase. The Beagle conflict was a border dispute between Chile and Argentina over the possession of Picton, Lennox and Nueva islands and the scope of the maritime jurisdiction associated with those islands that brought the countries to the brink of war in 1978. The 2001 Bangladesh-India border dispute conflict took place in the third week of April 2001 between troops of the Bangladesh Rifles (BDR) now it is known as Border Guard Bangladesh (BGB) and the Indian Border Security Force (BSF) on the poorly marked international border between the two countries. The Sutorina dispute was a border dispute between Montenegro and Bosnia and Herzegovina regarding the sovereignty over the territory of Sutorina.  Between the Berlin Congress of 1878 and the aftermath of World War II in 1947, the territory of Sutorina was a part of Bosnia and Herzegovina within Austria-Hungary and the first Yugoslavia, but then became part of the SR Montenegro within second Yugoslavia.  After the breakup of Yugoslavia, the territory was controlled by Montenegro, but some Bosnian officials have claimed that the territory transfer was illegal, disputing Montenegrin sovereignty over the area.  In 2015, two countries reached an agreement which gives the sovereignty over the territory to Montenegro. The Treaty of Dappes was concluded on 8 December 1862 between France and the Swiss Confederation.  Resolving a long-standing border dispute between the two countries, the accord awarded the Vallee des Dappes (which had been controlled by Switzerland since 1815) to France, in exchange for a comparable piece of territory just to the north.  The treaty is noteworthy for dividing the tiny village of La Cure between the two countries, with the new border bisecting not just the town itself, but several structures within it.
Answer: Chile and Argentina