10 Devastating Conflicts That Have Shaped the 21st Century

Some historians and researchers argue that humanity is living through an unusually peaceful period. Yet that claim can overlook the many conflicts the world has experienced since 2000.

Some of these wars began during the twentieth century but continued to shape the twenty-first. Others erupted more recently and remain unresolved. Together, they have produced mass death, displacement, famine, and documented atrocities that will affect survivors for generations.

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10 Tigray War

The Tigray War erupted in northern Ethiopia in November 2020 after years of tension between Prime Minister Abiy Ahmed’s federal government and the Tigray People’s Liberation Front. The TPLF had once dominated Ethiopia’s ruling coalition but lost much of its national influence after Abiy took office in 2018. Relations deteriorated further when Tigray held a regional election that the federal government had postponed because of the COVID-19 pandemic.

After Tigrayan forces attacked federal military bases, Abiy sent troops into the region. The conflict quickly expanded as Eritrean soldiers and forces from Ethiopia’s Amhara region joined the federal side. Tigrayan forces later pushed into neighboring regions before a government counteroffensive reversed many of their gains.

All sides were accused of atrocities, including massacres, sexual violence, forced displacement, and attacks on civilian infrastructure. Restrictions on food, medicine, and humanitarian assistance also contributed to famine-like conditions. Precise casualty figures remain fiercely disputed, but researchers have estimated hundreds of thousands of direct and indirect deaths. African Union mediator Olusegun Obasanjo later suggested that the toll may have reached 600,000.

The federal government and Tigrayan authorities signed the Pretoria peace agreement in November 2022, ending the worst of the fighting. However, incomplete implementation, unresolved territorial disputes, political divisions, and renewed clashes have left the region suspended between war and peace.^[1]

9 Sri Lankan Civil War

The Sri Lankan Civil War—fought primarily between the government and the Liberation Tigers of Tamil Eelam—lasted from 1983 to 2009. Since the country’s independence in 1948, its Sinhalese-dominated government had passed discriminatory measures affecting the Tamil population, contributing to protests and demands for equal rights. The LTTE formed in 1976 and eventually pursued an independent Tamil state through armed struggle.

The conventional beginning of the war came in 1983, when the LTTE killed thirteen Sri Lankan soldiers. The attack was followed by anti-Tamil pogroms known as Black July, during which hundreds of Tamils were killed and thousands of homes and businesses were destroyed. The violence helped turn a growing insurgency into a prolonged civil war.

The conflict produced mass civilian casualties and serious human rights abuses by both sides. Government forces were accused of indiscriminate shelling, enforced disappearances, torture, sexual violence, and extrajudicial killings. The LTTE employed suicide bombings, political assassinations, child soldiers, forced recruitment, and civilians as human shields.

The government defeated the LTTE in May 2009 after a final offensive that trapped large numbers of civilians in the shrinking combat zone. The exact death toll remains disputed, particularly for the war’s final months, but the United Nations estimates that between 80,000 and 100,000 people died during the twenty-six-year conflict.^[2]

8 Second Congo War

The Second Congo War—lasting officially from 1998 to 2003—grew from the regional turmoil surrounding the Rwandan genocide and the First Congo War. Congolese leader Laurent-Désiré Kabila had seized power in 1997 with support from Rwanda and Uganda, but relations soon deteriorated. In July 1998, Kabila ordered foreign troops to leave the Democratic Republic of the Congo.

A military rebellion erupted in August, supported by Rwanda and Uganda. Angola, Zimbabwe, and Namibia intervened on Kabila’s side, while numerous rebel organizations and foreign armies competed for territory, political influence, and access to the country’s mineral wealth. The involvement of so many governments and armed factions earned the conflict the nickname “Africa’s World War.”

Rwandan-backed forces advanced rapidly toward Kinshasa, but intervention by Angola and Zimbabwe stopped the assault on the capital in August 1998. Fighting continued across the vast country even after Laurent Kabila was assassinated in January 2001 and succeeded by his son, Joseph Kabila.

Peace agreements led to a transitional government and the formal end of the war in 2003, but armed violence continued in eastern Congo. Estimates of the death toll vary dramatically because most victims died from hunger, disease, and the collapse of medical services rather than direct combat. Conflict in the DRC since 1996 has been linked to approximately six million deaths, making it one of the deadliest crises since World War II.^[3]

7 Darfur Conflict

The conflict in Darfur began in 2003, when predominantly non-Arab rebel groups took up arms against the Sudanese government. The Sudan Liberation Army and Justice and Equality Movement accused President Omar al-Bashir’s government of politically and economically marginalizing the western region.

In response, the government armed and supported militias known collectively as the Janjaweed. These forces attacked communities believed to support the rebellion, burning villages, killing civilians, and committing widespread sexual violence. Government aircraft also bombed civilian areas. Hundreds of thousands died from violence, hunger, and disease, while millions were forced from their homes.

The United States characterized the campaign as genocide in 2004. The International Criminal Court later charged Bashir with genocide, crimes against humanity, and war crimes, although those charges have not resulted in a completed trial.

Darfur’s suffering did not end with Bashir’s removal in 2019. When another civil war erupted in Sudan in April 2023, the Rapid Support Forces—an organization with roots in the Janjaweed—renewed ethnically targeted attacks across the region. In 2025, the United States determined that RSF members had committed genocide in Darfur. More than two decades after the original rebellion, civilians remain trapped in another cycle of massacres, displacement, and famine.^[4]

6 Second Intifada

The Al-Aqsa Intifada—also known as the Second Intifada—was a Palestinian uprising that began in September 2000 and continued until approximately 2005. It followed the failure of peace negotiations, mounting frustration with the Oslo process, continued Israeli settlement expansion, and years of political tension.

Ariel Sharon’s visit to the site known to Muslims as Haram al-Sharif and to Jews as the Temple Mount provided the immediate spark. Palestinian demonstrations followed, and confrontations with Israeli security forces quickly became deadly. The violence soon expanded far beyond street protests.

Palestinian armed groups carried out shootings and suicide bombings against Israeli soldiers and civilians. Israel responded with military incursions, airstrikes, targeted killings, arrests, curfews, and extensive restrictions on Palestinian movement. Israel also began constructing its West Bank barrier during the uprising, arguing that it was necessary to prevent attacks.

The Second Intifada was far deadlier than the first. Approximately 3,000 Palestinians and 1,000 Israelis were killed, along with dozens of foreign nationals. Violence declined after Yasser Arafat died in 2004, the election of Mahmoud Abbas, and a 2005 summit at Sharm el-Sheikh, though no single event formally ended the conflict or resolved its underlying causes.^[5]

5 Second Sudanese Civil War

The Second Sudanese Civil War erupted in 1983 after the government dismantled southern autonomy established under the 1972 Addis Ababa Agreement. President Gaafar Nimeiry’s effort to impose sharia law across the religiously and ethnically diverse country further intensified the crisis. Disputes over political representation, oil, land, and economic marginalization also fueled the conflict.

The war primarily pitted the Sudan People’s Liberation Army against the government in Khartoum. Although fighting initially centered on southern Sudan, it eventually spread to areas such as the Nuba Mountains and Blue Nile. Both sides committed serious human rights abuses, including attacks on civilians and the recruitment of child soldiers.

A coup removed Nimeiry in 1985, and the succeeding government attempted to negotiate with the SPLA. Those efforts failed to end the war. Omar al-Bashir seized power in another coup in 1989, establishing an Islamist government and intensifying military operations during the 1990s.

The warring parties signed the Machakos Protocol in July 2002, creating the foundation for the Comprehensive Peace Agreement of January 9, 2005. The agreement established an autonomous southern region and provided for the referendum that eventually led to South Sudan’s independence in 2011. By then, approximately two million people had died from combat, famine, and disease, while more than four million had been displaced.^[6]

4 Syrian Civil War

The Syrian Civil War began in 2011, when the government of President Bashar al-Assad responded violently to demonstrations demanding political reform. Arrests, torture, and lethal force failed to suppress the protests. Instead, parts of the opposition took up arms, turning the uprising into a sprawling civil war.

The conflict soon involved a bewildering collection of government forces, rebel factions, Kurdish-led groups, Islamist organizations, and foreign powers. Iran and Russia supported Assad’s government, while Turkey, the United States, Gulf states, and others backed different opposition or local forces. The Islamic State exploited the chaos to seize large areas of Syria and Iraq before losing most of its territory.

Civilians endured sieges, indiscriminate bombing, chemical attacks, torture, executions, and deliberate assaults on hospitals and other essential infrastructure. More than 580,000 people were killed, while approximately thirteen million fled their homes or left the country. Tens of thousands more disappeared into government prisons.

Assad’s government collapsed in December 2024 after a rapid opposition offensive drove him from power. His fall ended one phase of the war but did not restore peace. Syria’s new authorities inherited a shattered economy, armed factions, foreign military involvement, unexploded weapons, sectarian tensions, and millions of displaced people. Fresh outbreaks of violence have demonstrated that removing one ruler cannot easily repair nearly fourteen years of destruction.^[7]

3 Boko Haram Insurgency

The Boko Haram insurgency in Nigeria has been ongoing since 2009. The extremist movement originated in northeastern Nigeria under Mohammed Yusuf, opposing Western-style education and the secular government while seeking to impose its interpretation of Islamic law.

Violence escalated dramatically in July 2009, when clashes with security forces led to hundreds of deaths. Police captured Yusuf and killed him in custody, but the movement soon re-emerged under Abubakar Shekau. In 2010, militants attacked a prison and freed hundreds of inmates. A year later, the group bombed the United Nations headquarters in Abuja, and coordinated attacks in Kano killed scores of people in January 2012.

Boko Haram drew worldwide condemnation after abducting 276 schoolgirls from Chibok in 2014. That same year, it seized territory and declared a caliphate. In 2015, the group pledged allegiance to ISIS, but it later fractured. The Islamic State West Africa Province emerged as a major rival to Shekau’s faction and developed its own network around the Lake Chad Basin.

Regional military offensives recaptured much of Boko Haram’s territory, but they did not end the insurgency. Boko Haram and ISWAP continue to attack civilians, military bases, villages, and infrastructure across Nigeria and neighboring countries. More than 40,000 people have died directly in the violence, while a United Nations study estimated that the wider conflict had caused nearly 350,000 direct and indirect deaths by the end of 2020.^[8]

2 Somali Civil War

The Somali Civil War grew from resistance to the repressive government of President Siad Barre during the 1980s. When armed factions overthrew Barre in January 1991, they failed to establish a replacement government. Rival warlords and clan militias instead fought over territory, ports, resources, and what remained of the state.

The collapse of central authority contributed to warfare, famine, and mass displacement. A United Nations intervention brought humanitarian relief but failed to create lasting stability. Numerous peace conferences and transitional governments followed, while regional authorities developed in Somaliland and Puntland. Somaliland declared independence in 1991 and achieved relative stability, but no country has formally recognized it as a sovereign state.

A new phase began in the 2000s with the rise of Islamist organizations. Al-Shabaab emerged as the most powerful insurgent group, fighting Somalia’s internationally supported governments and carrying out bombings and attacks throughout the region. African Union forces, Ethiopia, Kenya, the United States, and other foreign actors have all intervened.

Somalia established a permanent federal government in 2012, but political divisions, clan conflicts, and the al-Shabaab insurgency continue. Estimates of the overall death toll vary widely. Depending on whether famine and disease are included, the conflict and resulting collapse have killed between several hundred thousand and as many as one million people while displacing millions more.^[9]

1 Yemeni Civil War

While Yemen’s crisis has deeper roots, the current civil war began in 2014, when Houthi forces seized key areas, including the capital, Sana’a. The Houthis forced President Abdrabbuh Mansur Hadi from the capital and advanced south. In March 2015, a Saudi-led coalition intervened on behalf of his government, greatly expanding the conflict.

The war is not a simple struggle between two sides. The internationally recognized government transferred its authority to a Presidential Leadership Council in 2022, while southern separatists, local militias, al-Qaeda in the Arabian Peninsula, and other armed groups pursued their own agendas. Saudi Arabia, the United Arab Emirates, Iran, the United States, and additional foreign powers also became involved to varying degrees.

Coalition airstrikes killed civilians and destroyed homes, markets, hospitals, and infrastructure. Houthi forces launched indiscriminate attacks, recruited children, planted land mines, and restricted humanitarian assistance. Economic collapse, disrupted imports, damaged water systems, and reduced medical care produced hunger and disease across the country.

The United Nations estimated that the war had caused 377,000 direct and indirect deaths by the end of 2021, with most resulting from hunger, disease, and inadequate health care. A UN-brokered truce dramatically reduced fighting in 2022, but it did not produce a permanent peace agreement. Major hostilities erupted again in 2026, bringing renewed territorial offensives, airstrikes, attacks on Saudi Arabia, and the displacement of more than 100,000 additional people. After more than a decade, Yemen’s humanitarian catastrophe is once again intensifying.^[10]