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"The Arms Control Association’s work is an important resource to legislators and policymakers when contemplating a new policy direction or decision."

– General John Shalikashvili
former Chairman of the Joint Chiefs of Staff
Hotline Agreements

Last Reviewed: 
May 2020

Contact: Daryl Kimball, Executive Director, (202) 463-8270 x107

A hotline is a quick communication link between heads of states, which is designed to reduce the danger of an accident, miscalculation, or surprise attack, and especially an incident that might trigger a nuclear war.

1963 U.S.-Soviet Memorandum of Understanding
On June 20, 1963, the United States and the Soviet Union signed the "Memorandum of Understanding Between the United States of America and the Union of Soviet Socialist Republics Regarding the Establishment of a Direct Communications Link," also known as the hotline agreement. This agreement was designed to help speed up communications between the two governments and prevent the possibility of accidental nuclear war. It is no coincidence that the agreement came just a few months after the October 1962 Cuban missile crisis, when the United States and the Soviet Union came to the brink of nuclear conflict. The new agreement was designed to forestall such a crisis in the future.

The hotline agreement held each government responsible for the arrangements for the communications link on their territories respectively. The hotline would comprise of two terminal points, Washington and Moscow, with both a full-time duplex wire telegraph circuit with teletype equipment routed between the two points via London, Copenhagen, Stockholm, and Helsinki and a full-time duplex radiotelegraph routed between them through Tangier. In case the wire circuit was interrupted, messages would be transmitted via radio circuit.

American teleprinter machines were installed in the Kremlin to receive messages from Washington, which were in English; Soviet teleprinter machines were installed in the Pentagon to receive messages from Moscow, which were in Russian. Both nations also exchanged encoding devices in order to decipher the messages. The transmission of a message from one nation to another would take just a few minutes. The messages then were decoded and translated by the recipient country.

It is a misleading belief that the hotline was a red telephone that sat in the Oval Office of the White House. The first generation of the hotline had no voice element and actually resided in the National Military Command Center in the Pentagon. The countries decided against the use of a telephone as the leaders would rely too much on rapid translation, while using telegraphs instead would allow time to carefully read and then respond. The Washington–London link was originally carried over the Transatlantic No. 1 (TAT-1), the first submarine transatlantic telephone cable, which allowed the use of teleprinters. Such a design prevented spontaneous verbal communications, which could lead to misunderstanding and misperceptions.

First Use of the Hotline
The hotline significantly reduced the time required for direct communication between the heads of the two governments from hours to minutes. In August 1963, the system was ready to be tested. On August 30, 1963, the United States sent its first message to the Soviet Union over the hotline: "The quick brown fox jumped over the lazy dog's back 1234567890."

The message used every letter and number key on the teletype machine in order to see that each was in working order. The return message from Moscow was in Russian, but it indicated that all of the keys on the Soviet teletype were also functioning. After becoming operational that August, the direct communications link was tested every day.

The United States first used the hotline when President John F. Kennedy was assassinated on November 22, 1963. The hotline was next used in June 1967 during the Six Day War between Israel, Egypt, Jordan, and Syria to clarify the intentions of U.S. fleet movements in the Mediterranean that could have been interpreted as hostile. Thereby, the Soviet Union and the United States intended to reassure each other that they did not wish to be militarily involved in the crisis and did not make efforts to bring about a ceasefire. Throughout the duration of the Six Days War, the two sides used the hotline almost two dozen times for a variety of purposes. President Richard Nixon also used it during the Indo-Pakistani War of 1971 and again during the 1973 Arab-Israeli War. During the Reagan Administration, the hotline was used several more times. However, an official listing of the instances when the states used the hotline never has been released to the public.

Modern Version of U.S.–Russian Nuclear Hotline
In the 1970s, the hotline was improved with better technologies. On September 30, 1971, the two sides signed the hotline modernization agreement, which updated the hotline with two satellite communications circuits. Under this agreement, the United States was to provide one circuit via the Intelsat system, and the Soviet Union was to provide one circuit via its Molniya II system. The 1963 radio circuit was terminated, and the wire telegraph was retained as a back-up. The two satellite communications circuits became operational in January 1978.

In July 1984, the United States and the Soviet Union signed an accord to add a facsimile transmission capability to the hotline. This capability became operational in 1986.

The two countries in September 1987 signed an agreement creating the Nuclear Risk Reduction Centers (NRRC) in both Washington and Moscow, which became operational in 1988. Though using a similar communications system, the centers are separate from the hotline. While the hotline is reserved for heads of government, the centers exchange information and notifications as required under arms control and other confidence-building agreements.

Other Bilateral Hotline Agreements
Once the hotline between Washington and Moscow proved to be useful, other states established hotlines. In 1966, France signed an accord establishing a direct communications link between Paris and Moscow. Under the 1967 British-Soviet agreement, a direct communications line was set up between Moscow and London.

Russia–China Nuclear Hotline
In 1998, China established two head-of-state nuclear hotlines, one first with Russia and another with the United States.

In April 1996, during Russian President Boris Yeltsin’s third summit meeting in Beijing, the two sides agreed to maintain regular dialogues at various levels and through multiple channels, including a governmental telephone hotline. On May 3, 1998, a hotline between China and Russia officially began operating. This is the first time Beijing has established a hotline with the head of a foreign state. Ten years later, in March 2008, a hotline between the Chinese and Russian Defense Ministries was established to enhance bilateral cooperation between the two states. The Russian and Chinese were exchanging their views on the international and regional situation as well as other issues of common concern.

U.S.–China Nuclear Hotline
In April 1998, China’s Minister of Foreign Affairs Tang Jiaxuan and U.S. Secretary of State Madeleine Albright signed an agreement to establish a hotline between the governments of the two countries. The hotline was activated during President Clinton’s visit to China in June 1998.

India–Pakistan Nuclear Hotline
In June 2004, India and Pakistan agreed to set up a telephone nuclear hotline between the most senior officials in their foreign ministries in order to prevent a nuclear incident. The two countries also agreed to update an existing hotline between their respective directors of military operations and reaffirmed that each side would continue to uphold the moratorium on nuclear tests. A direct communications link between the two countries’ nuclear command authorities does not currently exist.

In 2011, India and Pakistan agreed to set up a “terror hotline” so as to allow Indian investigators to visit Pakistan in connection to the 2008 Mumbai attacks. The hotline warns each party state of possible militant attacks and moves them to restore the trust between each other.

North Korea-South Korea Hotline
The Seoul-Pyongyang “hotline” comprises 33 telephone lines that connect North and South Korea through the Panmunjom Joint Security Area within the Demilitarized Zone. Five are used for daily communications, 21 for negotiations, and 7 for transportation and commerce.

The first hotline, established in September 1971, was designed to allow the North and South Korean Red Crosses to negotiate. The two countries agreed to build more telephone connections in a July 4, 1972, Joint Communiqué. North Korea has periodically stopped responding to phone calls when tensions have spiked between the two countries. The most recent disconnection began in February 2016, after South Korea closed a jointly-operated manufacturing park in the Kaesong Industrial Region in response to North Korean missile testing.

On January 3, 2018, North Korean officials responded to a phone call on a Panmunjom hotline from South Korea, breaking the two-year silence. Earlier in the day, North Korea announced the channel would be reopened, and the South’s Ministry of Unification later confirmed that they had held a 20-minute phone conversation.

Two months later, at talks in Pyongyang on March 5, 2018, delegations from North and South Korea reached an agreement to reopen the first hotline between the presidents of each country, Kim Jong Un and Moon Jae-in. The hotline between the leaders went live on April 20, 2018.

South Korea–China Defense Hotline
In 2008, South Korea and China set up telephone hotlines between their navies and air forces to help prevent accidental clashes. However, the hotline has reportedly been used only a handful of times, and never to test procedures in a simulated crisis. South Korea and China agreed in July 2014 to establish an additional high-level hotline between their defense chiefs in an effort to strengthen military cooperation. The first call reportedly took place in December 2015.

India-China Hotline
In April 2010, the prime ministers of China and India agreed to set up a hotline between them in order to better avoid flare-ups over a longstanding border dispute across the Himalayas and strengthen their diplomatic ties. "The agreement to establish a hotline is an important confidence-building measure and it opens up a direct channel of communication between the two leaders," Nirupama Rao, India’s foreign secretary at the time, told reporters at a press conference in Beijing.

In 2018, China and India decided to establish another hotline between their armies. India stated in January 2020 that the line would soon become operational.

Vietnam-China Hotline
A hotline between the Vietnamese and the Chinese Ministries of Foreign Affairs opened in March 2012. In their talk on the line, the ministers affirmed their will to strengthen the Vietnam-China comprehensive strategic cooperative partnership.

Taiwan-China Hotline
In November 2015, the presidents of China and Taiwan agreed to establish a hotline between their respective chiefs of cross-Strait affairs. The line became operational a month later.