Anti-war movement
: 109–110 : 85, 89–90  Her arrest and lack of a trial sparked Bella Abzug and WILPF members to write to the United States Congress and petition President Richard Nixon to appeal to South Vietnamese officials for her release,: 126 : 90  which was widely covered in the press. Campaigns opposing the war and conscription also took place in Australia.

South African Border War: Opposition to the South African Border War spread to a general resistance to the apartheid military. Organizations such as the End Conscription Campaign and Committee on South African War Resisters, were set up. Many opposed the war at this time.

Yugoslav Wars: Following the rise of nationalism and political tensions after Slobodan Milošević came to power, as well as the outbreaks of the Yugoslav Wars, numerous anti-war movements developed in Serbia. The anti-war protests in Belgrade were held mostly because of opposition the Battle of Vukovar, Siege of Dubrovnik and Siege of Sarajevo, while protesters demanded the referendum on a declaration of war and disruption of military conscription.
More than 50,000 people participated in many protests, and more than 150,000 people took part in the most massive protest called "The Black Ribbon March" in solidarity with people in Sarajevo. It is estimated that between 50,000 and 200,000 people deserted from the Yugoslav People's Army, while between 100,000 and 150,000 people emigrated from Serbia refusing to participate in the war. According to professor Renaud De la Brosse, senior lecturer at the University of Reims and a witness called by the International Criminal Tribunal for the former Yugoslavia (ICTY), it is surprising how great the resistance to Milošević's propaganda was among Serbs, given that and the lack of access to alternative news.
The most famous associations and NGOs who marked the anti-war ideas and movements in Serbia were the Center for Antiwar Action, Women in Black, Humanitarian Law Center and Belgrade Circle. The Rimtutituki was a rock supergroup featuring Ekatarina Velika, Električni Orgazam and Partibrejkers members, which was formed at the petition signing against mobilization in Belgrade.
NATO bombing of Yugoslavia during the Kosovo War triggered debates over the legitimacy of the intervention. About 2,000 Serbian Americans and anti-war activists protested  in New York City against NATO airstrikes, while more than 7,000 people protested in Sydney. The most massive protests were held in Greece, and demonstrations were also held in Italian cities, London, Moscow, Toronto, Berlin, Stuttgart, Salzburg and Skopje.

2001 Afghanistan War: There was initially little opposition to the 2001 Afghanistan War in the United States and the United Kingdom, which was seen as a response to the 11 September 2001 terrorist attacks and was supported by most of the American public. Most vocal opposition came from pacifist groups and groups promoting a left-wing political agenda. Over time, opposition to the war in Afghanistan has grown more widespread, partly as a result of weariness with the length of the conflict and partly as a result of a conflating of the conflict with the unpopular war in Iraq.

Iraq War: The anti-war position gained renewed support and attention in the buildup to the 2003 invasion of Iraq by the U.S. and its allies.  Millions of people staged mass protests across the world in the immediate prelude to the invasion, and demonstrations and other forms of anti-war activism have continued throughout the occupation. The primary opposition within the U.S. to the continued occupation of Iraq has come from the grassroots. Opposition to the conflict, how it had been fought, and complications during the aftermath period divided public sentiment in the U.S., resulting in majority public opinion turning against the war for the first time in the spring of 2004, a turn which has held since.
The American country music band Dixie Chicks opposition to the war caused many radio stations to stop playing their records, but who were supported in their anti-war stance by the equally anti-war country music legend Merle Haggard, who in the summer of 2003 released a song critical of US media coverage of the Iraq War. Anti-war groups protested during both the Democratic National Convention and 2008 Republican National Convention protests held in Saint Paul, Minnesota, in September 2008.

Possible war against Iran: Organised opposition to a possible future military attack against Iran by the United States is known to have started during 2005–2006. Beginning in early 2005, journalists, activists and academics such as Seymour Hersh, Scott Ritter, Joseph Cirincione and Jorge E. Hirsch began publishing claims that United States' concerns over the alleged threat posed by the possibility that Iran may have a nuclear weapons program might lead the US government to take military action against that country in the future. These reports, and the concurrent escalation of tensions between Iran and some Western governments, prompted the formation of grassroots organisations, including Campaign Against Sanctions and Military Intervention in Iran in the US and the United Kingdom, to oppose potential military strikes on Iran. Additionally, several individuals, grassroots organisations and international governmental organisations, including the Director-General of the International Atomic Energy Agency, Mohamed ElBaradei, a former United Nations weapons inspector in Iraq, Scott Ritter, Nobel Prize winners including Shirin Ebadi, Mairead Corrigan-Maguire and Betty Williams, Harold Pinter and Jody Williams, Campaign for Nuclear Disarmament, Code Pink, the Non-Aligned Movement of 118 states, and the Arab League, have publicly stated their opposition to a would-be attack on Iran.

War in Donbass: Anti-war/Putin demonstrations took place in Moscow "opposing the War in Donbass", i.e., in Eastern Ukraine.

Saudi Arabian–led intervention in Yemen: 

2021 Israel–Palestine crisis: In May 2021, protests broke out following a flare-up of the Israel–Palestine conflict. In the U.S., thousands gathered in at least seven major cities across the country in solidarity with Palestinians. The 2021 conflict lasted from 6 May until 21 May when a ceasefire was signed. The following day, an estimated 180,000 protestors gathered in Hyde Park, England, in what may have been the largest pro-Palestine demonstration in British history. Speeches were made by anti-war campaigners and trade union members including demands that the UK government disinvest and sanction Israel. Messages such as "free Palestine" and "stop the war" were displayed on banners and placards and chanted by protesters. Despite the ceasefire, protests continued into June, with, for example, protestors in Oakland, California, attempting to block an Israeli cargo ship from entering the Port of Oakland on 4 June.

2022 Russian invasion of Ukraine: Beginning in 2022, the anti-war movement was renewed following tensions between Russia and Ukraine. Protests escalated on 24 February 2022, after Russia invaded Ukraine.
Russian President Vladimir Putin introduced prison sentences of up to 15 years for publishing "fake news" about Russian military operations. As of December 2022, more than 4,000 people, including Russian opposition politicians and journalists, had been prosecuted under Russia's "fake news" laws for criticizing the war in Ukraine.

2023 Israel–Hamas war: Multiple protests against the war took place around the world since the start of the 2023 Israel–Hamas war, in support of Palestine mostly.

Arts and culture: English poet Robert Southey's 1796 poem After Blenheim is an early modern example of anti-war literature that was written generations after the Battle of Blenheim but while Britain was again at war against France.
World War I produced a generation of poets and writers influenced by their experiences in the war. The work of poets, including Wilfred Owen and Siegfried Sassoon, exposed the contrast between the realities of life in the trenches and how the war was seen by the British public at the time and the earlier patriotic verse penned by Rupert Brooke. The German writer Erich Maria Remarque penned All Quiet on the Western Front, which has been adapted for several mediums and has become of the most often cited pieces of anti-war media.
Pablo Picasso's 1937 painting Guernica on the other hand, used abstraction, rather than realism, to generate an emotional response to the loss of life from the Condor Legion and Aviazione Legionaria's bombing of Guernica during the Spanish Civil War. The American author Kurt Vonnegut used science fiction themes in his 1969 novel Slaughterhouse-Five, depicting the bombing of Dresden in World War II, which Vonnegut witnessed.
The second half of the 20th century also witnessed a strong anti-war presence in other art forms, including anti-war music such as "Eve of Destruction", "And the Band Played Waltzing Matilda" and "One Tin Soldier", and films such as M*A*S*H and Die Brücke, opposing the Cold War in general or specific conflicts such as the Vietnam War. The war in Iraq has also generated significant artistic anti-war works, including the American filmmaker Michael Moore's Fahrenheit 9/11, which holds the box-office record for documentary films, and the Canadian musician Neil Young's 2006 album Living with War.

Anti-war intellectual and scientist-activists and their work: Various people have discussed the philosophical question of whether war is inevitable, and how it can be avoided; in other words, what are the necessities of peace.