Question: Operation Soberanía was a planned invasion due to a conflict over the possession of what islands?

Context paragraphs:
British anti-invasion preparations of 1803–05: British anti-invasion preparations of 1803–05 were the military and civilian responses in the United Kingdom to Napoleon's planned invasion of the United Kingdom.  They included mobilization of the population on a scale not previously attempted in Britain, with a combined military force of over 615,000 in December 1803.  Much of the southern English coast was fortified to repel a French landing.  However Napoleon never attempted his planned invasion and so the preparations were never put to the test.

Operation Downfall: Operation Downfall was the proposed Allied plan for the invasion of Japan near the end of World War II.  The planned operation was abandoned when Japan surrendered following the atomic bombings of Hiroshima and Nagasaki, the Soviet declaration of war and the Soviet invasion of Manchuria.  The operation had two parts: Operations Olympic and Coronet.  Set to begin in November 1945, Operation Olympic was intended to capture the southern third of the southernmost main Japanese island, Kyūshū, with the recently captured island of Okinawa to be used as a staging area.  Later, in the spring of 1946, Operation Coronet was the planned invasion of the Kantō Plain, near Tokyo, on the Japanese island of Honshu.  Airbases on Kyūshū captured in Operation Olympic would allow land-based air support for Operation Coronet.  If Downfall had taken place, it would have been the largest amphibious operation in history.

Operation Sea Lion (wargame): Operation Sea Lion was a major wargame conducted at Royal Military Academy Sandhurst in 1974.  Its aim was find out what might have happened had Nazi Germany launched Operation Sea Lion, their planned invasion of southeast England during World War II, in September 1940.  The wargame was organized by the "Daily Telegraph" and Dr Paddy Griffith from the Department of War Studies at Sandhurst.  The British umpires were Air Chief Marshal Christopher Foxley-Norris, Rear Admiral Teddy Gueritz and Major General Glyn Gilbert.  The German umpires were General Adolf Galland (air), Admiral Friedrich Ruge (naval) and General Heinrich Trettner (land).  After the game's conclusion, the umpires unanimously concluded that the invasion was a devastating defeat for the German invasion force.

Planned French invasion of Britain (1744): A planned invasion of Great Britain was to be undertaken by France in 1744 shortly after the declaration of war between them as part of the War of the Austrian Succession.  A large invasion force was prepared and put to sea from Dunkirk in February 1744, only to be partly wrecked and driven back into harbour by violent storms.  Deciding that circumstances were not favourable to an invasion, the French government suspended the attempt, and deployed their forces elsewhere.

Operation Soberanía: 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.

Operation Pastel: During World War II, Operation Pastel was the deception plan scheduled to protect Operation Olympic, the planned invasion of southern Japan.  Pastel would have falsely portrayed a threat of an American-led invasion against ports in China via attacks on Taiwan.  Parts of Operation Majestic, an operation declined due to Operation Olympic, were incorporated in Operation Pastel.

Beagle conflict: 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.

Papal mediation in the Beagle conflict: 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.

USNS Sgt. Curtis F. Shoup (T-AG-175): USNS "Sgt. Curtis F. Shoup" (T-AG-175) was a C1-M-AV1 coastal freighter.  Built as Spindle Eye, one of the many named for knots.  The ship, modified to be a "news transmission ship" for the press during the planned invasion of Japan, was completed 9 July 1945, delivered to the War Shipping Administration and placed under its agent Lykes Brothers Steamship Company the same day.  Days later, on 26 July, "Spindle Eye" was bareboat chartered to the War Department for operation by the Army.  The ship was renamed November 1947 by the Army, after serving as a radio relay ship at the Operation Crossroads atomic bomb tests and conversion to an Army passenger-cargo vessel, "Sgt. Curtis F. Shoup" in honor Sergeant Curtis F. Shoup who had been awarded the Medal of Honor.

Battle of Okinawa: The Battle of Okinawa (Japanese: 沖縄戦 , Hepburn: Okinawa-sen ) (Okinawan: 沖縄戦 , "Uchinaa ikusa " ), codenamed Operation Iceberg, was a major battle of the Pacific War fought on the island of Okinawa by United States Marine and Army forces against the Imperial Japanese Army and included the largest amphibious assault in the Pacific War during World War II, the April 1, 1945, invasion of Okinawa itself.  The 82-day battle lasted from April 1 until June 22, 1945.  After a long campaign of island hopping, the Allies were planning to use Okinawa, a large island only 340 mi away from mainland Japan, as a base for air operations for the planned invasion of the Japanese home islands.

Supporting paragraphs: Operation Soberanía Beagle conflict
Answer: Picton, Lennox and Nueva islands