Appeasement
As a result, they had mixed feelings towards the German and Italian regimes which had crushed the communists and socialists in their own countries".

Postwar politicians: Statesmen in the postwar years have often referred to their opposition to appeasement as a justification for firm, sometimes armed, action in international relations.

United States: U.S. President Harry S. Truman thus explained his decision to enter the Korean War in 1950, British Prime Minister Anthony Eden in his confrontation of Egyptian President Gamal Abdel Nasser in the Suez Crisis of 1956, U.S. President John F. Kennedy his "quarantine" of Cuba in 1962, U.S. President Lyndon B. Johnson in his resistance to communism in Indochina in the 1960s, U.S. President Ronald Reagan in his air strike on Libya in 1986, and U.S. President Donald Trump in the drone strike that led to the assassination of Qasem Soleimani in 2020.

Vietnam: After the Viet Minh won the Battle of Dien Bien Phu in 1954, U.S. President Dwight D. Eisenhower wrote in a letter to British Prime Minister Churchill, "We failed to halt Hirohito, Mussolini and Hitler by not acting in unity and in time. That marked the beginning of many years of stark tragedy and desperate peril. May it not be that our nations have learned something from that lesson?" Similarly, President Lyndon Johnson said to defend the Vietnam War, "Everything I knew about history told me that if I got out of Vietnam and let Ho Chi Minh run through the streets of Saigon, then I'd be doing exactly what Chamberlain did in World War II. I'd be giving a big fat reward to aggression".

Cuba: During the Cuban Missile Crisis, U.S. Air Force Chief of Staff Curtis LeMay and various hawks within the Kennedy administration for an air strike on Soviet nuclear missiles in Cuba compared Kennedy's hesitance to do so to appeasement. That was partially a jab at Kennedy's father Joseph P. Kennedy Sr., who had supported appeasement while he was U.S. Ambassador to the United Kingdom and later supported a negotiated surrender to Germany during the May 1940 War Cabinet Crisis and the Battle of Britain.

Soviet Union: During the Cold War, the "lessons" of appeasement were cited by prominent conservative allies of Reagan, who urged him to be assertive in "rolling back" Soviet-backed regimes throughout the world. The Heritage Foundation's Michael Johns, for instance, wrote in 1987 that "seven years after Ronald Reagan's arrival in Washington, the United States government and its allies are still dominated by the culture of appeasement that drove Neville Chamberlain to Munich in 1938." Some conservatives even compared Reagan to Chamberlain after his withdrawal of the Multinational Force in Lebanon because of the 1983 Beirut barracks bombing.

Argentina: British Prime Minister Margaret Thatcher invoked the example of Churchill during the Falklands War of 1982: "When the American Secretary of State, Alexander Haig, urged her to reach a compromise with the Argentines she rapped sharply on the table and told him, pointedly, 'that this was the table at which Neville Chamberlain sat in 1938 and spoke of the Czechs as a faraway people about whom we know so little'". Thatcher, along with U.S. National Security Advisor Brent Scowcroft, made similar arguments after the 1990 Iraqi invasion of Kuwait and the planning for the Gulf War. The spectre of appeasement was raised in discussions of the Yugoslav wars of the 1990s.

Iraq: U.S. President George W. Bush and British Prime Minister Tony Blair also cited Churchill's warnings about German rearmament to justify their action in the run-up to the 2003 Iraq War.

Syria: In 2013, Obama administration officials such as Secretary of State John Kerry and Secretary of Defense Chuck Hagel claimed that a failure of the United States to intervene in the Syrian Civil War after the Ghouta chemical attack would be an act of appeasement towards Bashar al-Assad.

Iran: In May 2008, U.S. President George W. Bush cautioned against "the false comfort of appeasement" when dealing with Iran and 
Iranian President Mahmoud Ahmadinejad. Opponents of President Barack Obama later criticized the Joint Comprehensive Plan of Action as an act of appeasement with Iran. U.S. Secretary of State Mike Pompeo later stated that the Trump administration's foreign policy was "trying to correct for what was the Obama administration's appeasement of Iran."

Islamism: The Dutch politician Ayaan Hirsi Ali demands a confrontational policy at the European level to meet the threat of radical Islam and compares policies of non-confrontation to Neville Chamberlain's appeasement of Hitler.

China: Tibetan separatists consider the policy of the West towards the People's Republic of China with regard to Tibet as appeasement.

Russia: The minimal international reactions to the invasion of Chechnya, the invasion of Georgia and the 2014 annexation of Crimea, as well as the conflict in the Donbas, which all stand in violation of international law, is seen by some as the cause that encouraged Russian president Vladimir Putin to conduct a full-scale invasion of the rest of Ukraine in 2022.
Some commentators have suggested that some NATO countries are following the policy of appeasement towards Vladimir Putin's Russia by rejecting the support of Ukrainian democracy through military operations and aid during the 2022 Russian invasion of Ukraine.

North Korea: 

Afghanistan: The 2020 Doha Agreement between the United States and the Taliban without involvement of the then Afghan government was criticized as the American appeasement of the Taliban. Over the American war in Afghanistan, the United States and its NATO allies (ISAF and RSM periods) along with the government of the Islamic Republic of Afghanistan and its national defense and security forces warred against the Taliban and its allied militant groups and later the Islamic State – Khorasan Province. After Donald Trump become the president, he decided to wrap up all military operations in Afghanistan and to begin negotiation with the Taliban, which culminated with the Doha Agreement on 29 February 2020. After President Joe Biden decided to withdraw all American troops from  Afghanistan on 31 August 2021, the Taliban launched their final offensive of the war, which brought the fall of the Islamic Republic of Afghanistan, during which Kabul was taken over by the Taliban on 15 August 2021. The United States completed its withdrawal from Afghanistan and the evacuation of American citizens and residents and at-risk Afghans from Kabul International Airport on 30 August 2021.

Criticism: In the mid-20th century, appeasement was seen as discredited in the United Kingdom due to its role in contributing to World War II.
Scholar Aaron McKeil pointed out that appeasement restraint against liberal interventionism would lead to more proxy wars, and fail to offer institutions and norms for mitigating great power conflict. Alternative strategies to avoid conflict include deterrence, where threats or limited force dissuades an actor from escalating conflict, typically because the prospective attacker believes that the probability of success is low and the costs of attack are high.
Appeasement can be seen as promoting frozen conflicts and rewarding aggression.
Appeasement might be more difficult to achieve if the source of conflict is indivisible and can be held by only one party, preventing small concessions.
The case of peacebuilding in Timor-Leste can be seen as appeasement to avoid conflict without addressing underlying conflict grievances.
The Minsk agreements have been called by some as appeasement, which subsequently failed to prevent the 2022 Russian invasion of Ukraine.
Appeasement can face the dilemma where appeasing a group of former rebels can increase grievances with new groups.

See also: 

Notes: 

References: 

Sources: Grant Duff, Sheila (1938). Europe and the Czechs. London: Penguin.

Further reading: 

Historiography: Barros, Andrew, Talbot C. Imlay, Evan Resnick, Norrin M. Ripsman, and Jack S. Levy. "Debating British Decision-making toward Nazi Germany in the 1930s." International Security 34#1 (2009): 173–98.  online.
Cole, Robert A. "Appeasing Hitler: The Munich Crisis of 1938: A Teaching and Learning Resource," New England Journal of History (2010) 66#2 pp. 1–30.
Dimuccio, Ralph BA. "The study of appeasement in international relations: Polemics, paradigms, and problems." Journal of peace research 35.2 (1998): 245–259.
Finney, Patrick. "The romance Of decline: The historiography of appeasement and British national identity." Electronic Journal of International History 1 (2000). online; comprehensive evaluation of the scholarship
Hughes, R. Gerald. "The Ghosts of Appeasement: Britain and the Legacy of the Munich Agreement." Journal of Contemporary History (2013) 48#4 pp. 688–716.
Record, Jeffrey. "Appeasement Reconsidered – Investigating the Mythology of the 1930s" (Strategic Studies Institute, 2005)  online
Roi, Michael. "Introduction: Appeasement: Rethinking the Policy and the Policy-Makers." Diplomacy and Statecraft 19.3 (2008): 383–390.
Strang, G. Bruce.