Mr. Horn was the communist regime’s last foreign minister and later embraced free-market policies, including the sale of state assets to foreign investors, as premier from 1994 to 1998.
Mr. Horn’s journey took him from young communist militant aiding Soviet troops in crushing Hungary’s uprising in 1956 to top diplomat helping usher the country out of Moscow’s sphere of influence and on a path to membership in the European Union and NATO.
His defining moment came on June 27, 1989, when he joined Austrian Foreign Minister Alois Mock in cutting the fence separating the two countries, presaging the end of the Cold War.
The cutting ceremony, captured by television cameras, prompted tens of thousands of East Germans to go to Hungary in the hope of crossing over to Austria and then joining relatives in West Germany.
Lost in the symbolism of the event was the fact that the ministers actually cut the only remaining section of the Iron Curtain on the border; the decision to disassemble the physical barrier had been made and carried out earlier. The images also were misleading because no official decision had been taken by Hungary to open its western border.
“They actually had to rebuild the fence on a 200-meter section so that they’d have something to cut through,” Miklos Nemeth, Hungary’s prime minister at the time, said in a 2009 interview with Naplo Online. “The only significance of that was that we could further test the tolerance” of the Soviets.
It worked. The first East German refugees crossed into Austria from Hungary on Aug. 19, 1989, during a civic gathering on the border that came to be known as the Pan-European Picnic. Tens of thousands followed after Sept. 10, 1989, when Mr. Horn announced on the evening news that Hungary would officially open its border the following day. The Berlin Wall came down two months later.
After Hungary’s transition to democracy, Mr. Horn helped lead the Socialist Party, the successor to the communists, to power in 1994.
As premier, Mr. Horn sold state companies, devalued the currency, restricted imports and lured foreign investment, boosting growth and winning approval from business executives but alienating many voters, who were jolted by the vanishing social safety net they had grown accustomed to during four decades of communist rule.
“We are wiping away the last remnants of Kadarism and putting an end to the patronizing role of the state,” Mr. Horn wrote in Time magazine in 1996, in reference to longtime communist leader Janos Kadar. He added that he had turned into “a European left-wing politician” and called the communist system “antidemocratic, against achievement and performance.”
Gyula Horn was born July 5, 1932, into a poor, working-class family in Budapest. He started working as a fifth-grader to make ends meet, according to his official biography on the parliament’s Web site. His father was killed in 1944 by the Gestapo, the secret police of Nazi Germany, with which Hungary was allied during World War II.
In the 1956 anti-Soviet uprising, which started as a student movement and was later joined by Hungary’s reformist communist government, Mr. Horn backed the Soviets, joining a local militia to put down the revolt. The same year, he became a member of the Communist Party, led by Kadar, who was installed by Moscow and ruled Hungary until 1988.
Mr. Horn started his career in the Finance Ministry. He moved to the Foreign Ministry in 1959 and rose through the ranks, holding diplomatic postings in Eastern Europe.
While not image-conscious — Mr. Horn was a chain smoker, tended to mumble and wore a head brace for months after a car accident in 1994 — he cultivated his place in history as the leader who pierced the Iron Curtain, drawing criticism from historians and peers for inflating his role.
In the Naplo interview, Nemeth said he traveled to Moscow four months before the symbolic fence-cutting ceremony in 1989 and told Soviet leader Mikhail Gorbachev that the border with Austria would be opened. The dismantling started immediately after his return, Nemeth said.
The official opening of the border, in September, was delayed by a few days because Nemeth rescheduled it after officials, including Mr. Horn, leaked the date, Naplo said.
“Gyula was desperate. He thought that meant he wouldn’t be the one making the announcement,” Nemeth said, according to Naplo. “I calmed him down and said I’d keep my promise.”
In 1990, Mr. Horn was awarded the Charlemagne Prize, presented to individuals for the “most valuable contribution in the services of Western European understanding and work for the community, and in the services of humanity and world peace.”
The last public event Mr. Horn attended was a 2007 party for his 75th birthday in Budapest, where Gorbachev was among the guests. Days earlier, then-President Laszlo Solyom rejected giving a state award to Mr. Horn, citing the former premier’s lack of remorse about his actions in the anti-Soviet uprising.
Survivors include his wife, the former Anna Kiraly, and two children.
— Bloomberg News