An American infantry patrol walks through the ruins of the French town of Saint-Lo, after it was captured from Germans in the Battle of Normandy in July 1944.

Wars between countries are among the greatest threats to world order. Throughout history, they have killed tens of millions of people, displaced entire communities, caused trillions of dollars of destruction, and contributed to the spread of hunger, poverty, and disease.

When countries come into conflict with one another, this is known as interstate conflict. In general, costly interstate wars have been declining since World War II. However, that trend does not mean countries peacefully coexist or that the threat of full-scale war has disappeared.

This resource explains the decline in interstate war, breaks down the ways countries continue to fight each other, and explores how two of the world’s most powerful countries—the United States and China—are sliding into conflict without having fired a single bullet

Why has interstate war become less common?

For one, the potential devastation of war has increased since the introduction of nuclear weapons at the end of World War II. Nuclear-armed powers launching a full-scale war today could spell the end of civilization itself.

Further, powerful alliances like the NATO serve as credible deterrents to interstate war, and international institutions such as the United Nations provide forums for countries to resolve disputes without resorting to fighting. However, the fact that those institutions cannot fully prevent conflicts—for example, the ongoing war in Ukraine—is noteworthy.

Some political scientists attribute that trend to the worldwide increase in democracies, with certain experts arguing that democracies are less likely to fight one another and that accountable leaders are less willing to wage potentially costly and unpopular wars. Other experts believe that an increase in international trade has made the world a safer place, as economically interdependent countries are less apt to go to war.

What types of conflict occur between countries?

The world is far from a harmonious place, and countries continue to try to increase their power, undermine their rivals, and advance their national interests. In some cases, violent interstate conflict occurs but stops short of an all-out war. In other instances, countries battle for influence through a range of economic, diplomatic, and cyber tools. Though those forms of conflict can be less violent than conventional war, they still pose considerable risks to people and their governments.

Security officer standing watch in front of shipping containers and machinery at a port.

Armed Force

Armed force involves a country or another entity using human and financial resources to use violence to influence a situation and pursue objectives. In recent years, for instance, Russia used armed force to annex Ukraine’s Crimean Peninsula, resulting in escalating violent warfare between Russia and Ukraine. Similarly, China continues to threaten to use force to achieve unification with Taiwan. The United States has also used armed force to pursue various interests abroad, including combating terrorist threats, addressing humanitarian crises, and ousting unfavorable regimes. Military operations can also be conducted in self-defense, to stem civil unrest and to secure access to resources—among other objectives.


Countries can use technology to attack an adversary’s infrastructure and vital facilities, including its energy grid, communications network, and banking infrastructure. Cyberattacks allow countries to attack opponents covertly, from far away, and at relatively low risk. Israel, for instance, has reportedly launched cyberattacks on the nuclear enrichment facilities of its adversary Iran and shut down computer systems at a major Iranian port.


Sanctions are economic penalties countries use to compel people, companies, and other governments to change their behavior on a broad range of issues, including nuclear proliferation and human rights. Although sanctions are seen as low-cost alternatives to war, they can still have devastating consequences by cutting off countries’ access to food, energy, and financial resources. U.S. sanctions on Cuba are estimated to have cost the country approximately $130 billion over the last sixty years—a figure far larger than Cuba’s entire economy ($100 billion in 2018). Still, although sanctions can accomplish modest objectives, they rarely force a country to fundamentally change course. Cuba’s communist government has endured in the face of massive U.S sanctions, as has Iran’s revolutionary government and North Korea’s brutal dictatorship.

Trade War

Tariffs (taxes on imports) or quotas (hard limits on how much of a particular product a country can import) are two tools governments can use to give their domestic industries a leg up on foreign competition or punish other countries for political reasons. Those actions, however, are often costly for both sides, as they limit an exporting country’s ability to sell products and can also make goods more expensive for importing countries. Japan and South Korea are mired in a trade war that has economically harmed both sides as well as other countries that rely on free-flowing Asian supply chains for the cheap production of electronics like cell phones and computers.

Proxy War

Rather than wage war directly, powerful countries can fight one another indirectly by funding or arming opposing sides in a third country. Although those interventions can limit the costs of war and the number of citizen deaths for those powerful countries, they can also turn wars into far larger and deadlier affairs for countries where the fighting is occurring. The Middle East is home to several proxy wars in which countries—most notably rivals Iran and Saudi Arabia—fund, train, and equip opposing sides in various conflicts. Although the two regional powers have largely refrained from attacking each other directly, their involvement in those local battles has contributed to hundreds of thousands of deaths in Syria and driven millions of people to the brink of starvation in Yemen.

Black smoke spews out of the mouth of a Saudi artillery cannon as it fires toward Houthis.

Domestic Destabilization

Governments can directly interfere in another country’s internal affairs by supporting—or even arming—opposition, separatist, or terrorist groups to promote instability within an adversary’s borders. This destabilization is often done through intelligence gathering and covert actionIndia and Pakistan, for example, have long accused each other of backing separatist groups in restive areas of their respective countries.

Electoral Interference

Countries can attempt to influence elections in other countries to support their preferred candidate or simply to sow mistrust in an electoral process. Russian election interference in the United States, France, and Germany has been well documented. But other countries interfere in elections too. In 2017,Turkish President Recep Tayyip Erdogan publicly encouraged more than one million Germans of Turkish descent to vote against two German parties, calling them “enemies of Turkey.”

Diplomatic Conflict

Countries can try to punish or isolate other governments by limiting or even cutting off diplomatic relations. Diplomatic conflict can take the form of expelling another government’s diplomats or ordering the closure of that country’s consulates or embassies. Countries including Bahrain, Egypt, Saudi Arabia, and the United Arab Emirates cut ties with Qatar in 2017 over accusations of funding terrorism. Those governments closed Qatar’s embassies in their countries and banned Qatari planes from using their airspace, while Saudi Arabia sealed off Qatar’s only land border. Those actions could cost Qatar billions of dollars.

Environmental Conflict

Countries can manipulate shared ecosystems—like rivers and forests—to benefit themselves or deliberately harm neighbors. Such environmental conflict can contribute to food and water shortages, particularly as global temperatures rise and ecosystems become increasingly vulnerable. Ethiopia’s construction of a hydroelectric dam on the Nile River threatens Egypt’s vital water source, which supports nearly all of the country’s one hundred million residents. So serious is the threat that Egypt has threatened military action to halt the dam’s construction.

Egyptians fishing on small boats.

How are the United States and China in conflict?

Even if not at war, the United States is in conflict with various countries. It levies sanctions against Cuba, Iran, and North Korea, bears the brunt of election interference from Iran and Russia, and backs opponents of Syrian President Bashar al-Assad and Venezuelan President Nicolás Maduro. The United States and China have not directly fought each other since the Korean War, but the world’s two largest economies have come into conflict in several costly ways.

The two countries are embroiled in a trade war, with the United States accusing China of stealing intellectual property from American companies and violating the commitments it made when it joined the World Trade Organization (WTO). Similarly, China accuses the United States of not upholding its own WTO commitments. Since 2018, the United States has imposed tariffs on a wide variety of Chinese goods, and China retaliated with tariffs of its own. As a result, goods are more expensive for consumers in both countries, while exporters have been harmed. 

The trade war is closely related to escalating technology competition between the two countries. Citing national security risks, the United States banned China’s largest telecommunications company, Huawei, from building 5G wireless networks in the United States and announced sanctions on foreign companies that sell certain technology to Huawei. The United States has similarly cited national security concerns in attempting to ban popular Chinese-owned applications like TikTok and WeChat. Meanwhile, China has prohibited large U.S. technology companies—including Facebook, Google, and Twitter—from operating in China given their potential to enable political dissent and instability.

In 2020, the United States also placed economic sanctions on Chinese companies and political leaders linked to human rights violations in China’s Xinjiang region, where the Chinese government has detained over one million ethnic Uyghurs and other Muslim minorities in so-called reeducation camps. Those sanctions restrict targeted companies from buying American technology and ban several senior officials and their families from entering the United States or accessing assets they own in the country.

The United States and China have also traded accusations of meddling in the other’s domestic affairs. China claims the United States is destabilizing the political situation in Hong Kong by supporting pro-democracy protesters. The United States, meanwhile, has accused China of repeatedly attempting to influence U.S. elections.

Additionally, members of the Chinese military have carried out cyberattacks on U.S. government agencies and companies. In a 2017 attack on the American credit agency Equifax, hackers stole the social security numbers of over 145 million Americans. Concerns about escalating cyberwarfare boiled over into a diplomatic conflict in 2020 when the United States ordered China to close its consulate in Houston over allegations of Chinese diplomats spying and aiding in the theft of U.S. intellectual property. In retaliation, China shuttered the U.S. consulate in Chengdu, cutting off U.S. access to nearby Tibet, where the United States has long accused China of human rights violations.

None of those issues has devolved into all-out war, but the world’s two most powerful economies locked in conflict has serious implications for world order and hundreds of billions of dollars in trade. Further, the increasing tensions that come with each instance of economic, political, cyber, and diplomatic conflict raise the likelihood that some flash point could become the tipping point for war. Any Chinese aggression against Taiwan (a democratic self-ruling island that China claims as its own), in the South China Sea (an area where China’s expansive claims to islands conflict with those of U.S. allies), or in the Senkaku Islands (which China claims but the United States recognizes as Japanese territory) could lead the two global powers into a far more violent stage in their ongoing rivalry.

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