Post–Cold War era

The  post –Cold War era is a period of history that follows the end of the Cold War, which represents history after the dissolution of the Soviet Union in December 1991. This period saw many former Soviet republics become sovereign nations, as well as the introduction of market economies in eastern Europe. This period also marked the United States becoming the world's sole superpower.

Relative to the Cold War, the period is characterized by stabilization and disarmament. Both the United States and Russia significantly reduced their nuclear stockpiles. The former Eastern Bloc became democratic and was integrated into world economy. Most of former Soviet satellites and three former Baltic Republics were integrated into the European Union and NATO. In the first two decades of the period, NATO underwent three series of enlargement and France reintegrated into the NATO command.

Russia formed Collective Security Treaty Organization to replace the dissolved Warsaw Pact, established strategic partnership with China and several other countries, and entered the non-military organizations SCO and BRICS. Both latter organizations included China, which is a fast rising power. Reacting on the rise of China, the Obama administration rebalanced strategic forces to the Asia-Pacific region.

Major crisis of the period included the Gulf War, Yugoslav Wars, the First and Second Congo Wars, First and Second Chechen War, September 11 attacks, War in Afghanistan (2001–2021), Iraq War, Russo-Georgian War and the ongoing Russo-Ukrainian War. Some have commented that the Israel-Hamas War has reignited the rhetoric of the War on Terror in a way not seen since the 2000s.

Background
Faced with the threat of growing German and Italian fascism, Japanese Shōwa statism, and a world war, the Western Allies and the Soviet Union formed an alliance of necessity during World War II. After the Axis powers were defeated, the two most powerful states in the world became the Soviet Union and the United States. Both federations were called the world's superpowers. The underlying geopolitical and ideological differences between the recent allies led to mutual suspicions and shortly afterward, they led to confrontation between the two, known as the Cold War, which lasted from about 1947 to 1991. It began with the second Red Scare and it ended with the fall of the Soviet Union, but some historians date the end of the Cold War to the Revolutions of 1989 or they date it to the signing of the world's first nuclear disarmament treaty, which occurred in 1987.

Ronald Reagan's campaign for the U.S. presidency in 1980 was focused on the rebuilding of the country. Over the next couple of years, the economy was recovering, new foreign policies were implemented, and the market was booming with independence. By contrast, the Soviet Union's economy was declining, its military power was declining, and the Soviet leaders overestimated the amount of influence which they had in the world. The United States' newfound superpower status allowed American authorities to better engage in negotiations with the Soviet, including terms that would favor the U.S. According to Chairman of the Presidium of the Supreme Soviet Leonid Brezhnev (in office 16 June 1977 – 10 November 1982), reducing the tension between the US and USSR was necessary in order to focus on fixing economic issues in the USSR. He theorized that rebuilding the USSR would ensure greater economic competition with the US.

At the dawn of the post–Cold War era, the Cold War historian John Lewis Gaddis wrote that the characteristics of the new era are not yet certain but he was certain that the characteristics of it would be very different from the characteristics of the Cold War era, which meant that a turning point of world-historical significance took place: "The new world of the post–Cold War era is likely to have few, if any, of these [Cold War] characteristics: that is an indication of how much things have already changed since the Cold War ended. We are at one of those rare points of 'punctuation' in history at which old patterns of stability have broken up and new ones have not yet emerged to take their place. Historians will certainly regard the years 1989–1991 as a turning point comparable in importance to the years 1789–1794, or 1917–1918, or 1945–1947; precisely what has 'turned,' however, is much less certain. We know that a series of geopolitical earthquakes have taken place, but it is not yet clear how these upheavals have rearranged the landscape that lies before us."

Subsequent events after the Cold War
During the Cold War, much of the policy and the infrastructure of the Western world and the Eastern Bloc had revolved around the capitalist and communist ideologies, respectively, and the possibility of a nuclear warfare. The end of the Cold War and the fall of the Soviet Union caused profound changes in nearly every society in the world. It enabled renewed attention to be paid to matters that were ignored during the Cold War and has paved the way for greater international cooperation, international organizations, and nationalist movements. The European Union expanded and further integrated, and power shifted from the G7 to the larger G20 economies.

The outcome symbolized a victory of democracy and capitalism which became a manner of collective self-validation for countries hoping to gain international respect. With democracy being seen as an important value, more countries began adopting that value. Communism ended also in Mongolia, Congo, Albania, Yugoslavia, Afghanistan, and Angola. As of 2023, only five countries in the world are still ruled as communist states: China, Cuba, North Korea, Laos, and Vietnam.

United States foreign policy changes
The United States, having become the only global superpower, used that ideological victory to reinforce its leadership position in the new world order. It claimed "the United States and its allies are on the right side of history." This new world order is referred to as "liberal hegemony" in international relations theory. Using the peace dividend, the United States military was able to cut much of its expenditure, but the level rose again to comparable heights after the September 11 attacks and the initiation of the War on Terror in 2001. Accompanying NATO expansion, Ballistic Missile Defense (BMD) systems were installed in Eastern Europe. However, from a relatively-weak developing country, China appeared as a fledgling emerging superpower. That created new potential for worldwide conflict. In response to the rise of China, the United States has strategically "rebalanced" to the Asia-Pacific region, though at the same time, began to retreat from international commitments.

Government, economic, and military institutions
The end of the Cold War also coincided with the end of apartheid in South Africa. Declining Cold War tensions in the later years of the 1980s meant that the apartheid regime was no longer supported by the West because of its anticommunism, but it was now condemned with an embargo. In 1990, Nelson Mandela was freed from prison and the regime began steps to end apartheid. This culminated in the first democratic elections in 1994, which resulted in Mandela being elected as President of South Africa.

Socialist and communist parties around the world saw drops in membership after the Berlin Wall fell, and the public felt that free-market ideology had won. Libertarian, neoliberal, nationalist and Islamist parties, on the other hand, benefited from the fall of the Soviet Union. As capitalism had "won," as people saw it, socialism and communism in general declined in popularity. Social Democrats in Scandinavia privatized many of their institutions in the 1990s, and a political debate on modern economics was reopened. Scandinavian nations are often now seen as social democrat (see Nordic model).

The People's Republic of China, which had started to move towards capitalism in the late 1970s and faced public anger after the Tiananmen Square protests of 1989 in Beijing, moved even more quickly towards free-market economics in the 1990s. McDonald's and Pizza Hut both entered the country in the second half of 1990, the first American chains in China, aside from Kentucky Fried Chicken, which had entered in 1987. Stock markets were established in Shenzhen and Shanghai in late 1990 as well. Restrictions on car ownership were loosened in the early 1990s and caused the bicycle to decline as a form of transport by 2000. The move to capitalism has increased the economic prosperity of China, but many people still live in poor conditions and work for companies for very low wages and in dangerous and poor conditions.

Many other Third World countries had seen involvement from the United States and/or the Soviet Union, but solved their political conflicts because of the removal of the ideological interests of those superpowers. As a result of the apparent victory of democracy and capitalism in the Cold War, many more countries adapted these systems, which also allowed them access to the benefits of global trade, as economic power became more prominent than military power in the international arena. However, as the United States maintained global power, its role in many regime changes during the Cold War went mostly officially unacknowledged, even when some, such as El Salvador and Argentina, resulted in extensive human rights violations.

Technology
The end of the Cold War allowed many technologies that had been off limits to the public to be declassified. The most important of these is the Internet, which was created as ARPANET by the Pentagon as a system to keep in touch after an impending nuclear war. The last restrictions on commercial enterprise online were lifted in 1995. The commercialization of the Internet and the growth of the mobile phone system increased globalization (as well as nationalism and populism in reaction).

In the years since then, the Internet's population and usefulness have grown immensely. Only about 20 million people (less than 0.5 percent of the world's population at the time) were online in 1995, mostly in the United States and several other Western countries. By the mid-2010s, more than a third of the world's population was online.

Further research continued into other Cold War technologies with the declassification of the Internet. While Reagan‘s Strategic Defense Initiative proved untenable in its original form, the system lives on in a redesigned state as the Aegis Ballistic Missile Defense System (BMDS). Countermeasures such as BMDS continue to be explored and improved upon post Cold War, but are often criticized for being unable to effectively stop a full nuclear attack. Despite advances in their efficacy, Anti-ballistic missiles are often viewed as an additional piece to modern day diplomacy where concepts such as Mutual assured destruction (MAD) and treaties such as that between Ronald Reagan and Mikhail Gorbachev following their Reykjavík Summit.

Alongside continued research defensive countermeasures there has been a proliferation of nuclear weapons around the world. Many nations have acquired technology required to produce nuclear weapons since the end of the Cold War. Pakistan’s nuclear program acquired Centrifuges capable of enriching uranium in the 80‘s and in 1998 was able to conduct several underground tests. Today the United States, Russia, the United Kingdom, France, and China all possess nuclear weapons and have signed the Nuclear Non-Proliferation Treaty in an attempt to curb the spread of nuclear weapons. Pakistan, India, and North Korea are also in possession of nuclear technology but have not signed the Nuclear Non-Proliferation Treaty.

The Cold War brought with it increased research into radio technology as well as nuclear weapons. The success of Sputnik 1 lead to an increase funding for Radio telescopes such as Jodrell Bank Observatory for use in tracking Sputnik and possible nuclear launches by the Soviet Union. Jodrell Bank and other observatories like it have since been used to track Space probes as well as investigate Quasars, Pulsars, and Meteoroids. Satellites such as the Vela (satellite) that were originally launched to detect nuclear detonation following the Partial Nuclear Test Ban Treaty have been used since then to discover and further investigate Gamma-ray bursts.