Armed conflict in eastern Ukraine erupted in early 2014 following Russia’s annexation of Crimea. The previous year, protests in Ukraine’s capital, Kyiv, against Ukrainian President Viktor Yanukovych’s decision to reject a deal for greater economic integration with the European Union (EU) were met with a violent crackdown by state security forces. The protests widened, escalating the conflict, and President Yanukovych fled the country in February 2014.
One month later, in March 2014, Russian troops took control of the Ukrainian region of Crimea. Russian President Vladimir Putin cited the need to protect the rights of Russian citizens and Russian speakers in Crimea and southeast Ukraine. Russia then formally annexed the peninsula after Crimeans voted to join the Russian Federation in a disputed local referendum. The crisis heightened ethnic divisions, and two months later, pro-Russian separatists in the eastern Ukrainian regions of Donetsk and Luhansk held their own independence referendums.
Armed conflict in the regions quickly broke out between Russian-backed forces and the Ukrainian military. Russia denied military involvement, but both Ukraine and the North Atlantic Treaty Organization (NATO) reported the buildup of Russian troops and military equipment near Donetsk and Russian cross-border shelling immediately following Crimea’s annexation. The conflict transitioned to an active stalemate, with regular shelling and skirmishes occurring along frontlines separating Russian- and Ukrainian-controlled eastern border regions.
Beginning in February 2015, France, Germany, Russia, and Ukraine attempted to kickstart negotiations to bring an end to the violence through the Minsk Accords. The agreement framework included provisions for a ceasefire, withdrawal of heavy weaponry, and full Ukrainian government control throughout the conflict zone. Efforts to reach a diplomatic settlement and satisfactory resolution, however, were largely unsuccessful.
In April 2016, NATO announced the deployment of four battalions to Eastern Europe, rotating troops through Estonia, Latvia, Lithuania, and Poland to deter possible future Russian aggression elsewhere on the continent, particularly in the Baltics. In September 2017, the United States also deployed two U.S. Army tank brigades to Poland to further bolster NATO’s presence in the region.
In January 2018, the United States imposed new sanctions on twenty-one individuals—including a number of Russian officials—and nine companies linked to the conflict in eastern Ukraine. In March 2018, the U.S. Department of State approved the sale of anti-tank weapons to Ukraine, the first sale of lethal weaponry since the conflict began. In October 2018, Ukraine joined the United States and seven other NATO countries in a series of large-scale air exercises in western Ukraine. The exercises came after Russia held its own annual military exercises in September 2018, the largest since the fall of the Soviet Union.
In October 2021, months of intelligence gathering and observations of Russian troop movements, force build-up, and military contingency financing culminated in a White House briefing with U.S. intelligence, military, and diplomatic leaders on a near-certain mass-scale Russian invasion of Ukraine. The only remaining questions were when the attack would take place and whether the United States would be able to convince allies to act preemptively. Both were answered on February 24, 2022, when Russian forces invaded a largely unprepared Ukraine after Russian President Vladimir Putin authorized a “special military operation” against the country. In his statement, Putin claimed that the goal of the operation was to demilitarize and denazify Ukraine and end the alleged genocide of Russians in Ukrainian territory.
In the days and weeks leading up to the invasion, the Joe Biden administration made the unconventional decision to reduce information-sharing constraints and allow for the broader dissemination of intelligence and findings, both with allies—including Ukraine—and publicly. The goal of this strategy was to bolster allied defenses and dissuade Russia from taking aggressive action. Commercial satellite imagery, social media posts, and published intelligence from November and December 2021 showed armor, missiles, and other heavy weaponry moving toward Ukraine with no official explanation from the Kremlin. By the end of 2021, more than one hundred thousand Russian troops were in place near the Russia-Ukraine border, with U.S. intelligence officials warning of a Russian invasion in early 2022. In mid-December 2021, Russia’s foreign ministry called on the United States and NATO to cease military activity in Eastern Europe and Central Asia, commit to no further NATO expansion toward Russia, and prevent Ukraine from joining NATO in the future. The United States and other NATO allies rejected these demands and threatened to impose severe economic sanctions if Russia took aggressive action against Ukraine.
In early February 2022, satellite imagery showed the largest deployment of Russian troops to its border with Belarus since the end of the Cold War. Negotiations between the United States, Russia, and European powers—including France and Germany—failed to bring about a resolution. In late February 2022, the United States warned that Russia intended to invade Ukraine, citing Russia’s growing military presence at the Russia-Ukraine border. President Putin then ordered troops to Luhansk and Donetsk, claiming the troops served a “peacekeeping” function. The United States responded by imposing sanctions on the regions and the Nord Stream 2 gas pipeline a few days later. Nevertheless, just prior to the invasion, U.S. and Ukrainian leaders remained at odds regarding the nature and likelihood of an armed Russian threat, with Ukrainian officials playing down the possibility of an incursion and delaying the mobilization of their troops and reserve forces.
On February 24, 2022, during a last-ditch UN Security Council effort to dissuade Russia from attacking Ukraine, Putin announced the beginning of a full-scale land, sea, and air invasion of Ukraine targeting Ukrainian military assets and cities across the country. U.S. President Joe Biden declared the attack “unprovoked and unjustified” and issued severe sanctions against top Kremlin officials, including Putin and Russian Foreign Minister Sergey Lavrov; four of Russia’s largest banks; and the Russian oil and gas industry in coordination with European allies. On March 2, 141 of 193 UN member states voted to condemn Russia’s invasion in an emergency UN General Assembly session, demanding that Russia immediately withdraw from Ukraine.
Since the 2014 annexation of Crimea, Ukraine has also increasingly been the target of thousands of cyberattacks. In December 2015, more than 225,000 people lost power across Ukraine in an attack on electricity generation firms, and, in December 2016, parts of Kyiv experienced another power blackout following a similar attack targeting a Ukrainian utility company. In June 2017, government and business computer systems in Ukraine were hit by the NotPetya cyberattack, which has been attributed to Russia; the attack spread to computer systems worldwide and caused billions of dollars in damages. In February 2022, Ukrainian government websites, including the defense and interior ministries, banking sites, and other affiliated organizations were targeted by distributed denial-of-service attacks alongside the Russian invasion.
As the initial Russian invasion slowed, long-range missile strikes caused significant damage to Ukrainian military assets, urban residential areas, and communication and transportation infrastructure. Hospitals and residential complexes also sustained shelling and bombing attacks. In late March 2022, Russia announced that it would “reduce military activity” near Kyiv and Chernihiv. By April 6, Russia had withdrawn all troops from Ukraine’s capital region. In the aftermath of the Russian withdrawal from Kyiv’s surrounding areas, Ukrainian civilians described apparent war crimes committed by Russian forces, including accounts of summary executions, torture, and rape.
On April 18, Russia launched a new major offensive in eastern Ukraine following its failed attempt to seize the capital. By May, Russian forces took control of Mariupol, a major and highly strategic southeastern port city that had been under siege since late February. Drone footage published by Ukraine’s far-right Azov Battalion revealed the brutality of the Russian offensive, which had reduced the city to rubble and caused a massive humanitarian crisis. Indiscriminate and targeted attacks against civilians in the city, including an air strike on a theater and the bombing of a maternity hospital, also amplified allegations against Russian forces for international humanitarian law violations.
Since the summer of 2022, fighting has largely been confined to Ukraine’s east and south, with Russian cruise missiles, bombs, cluster munitions, and thermobaric weapons devastating port cities along the Black Sea and the Sea of Azov. The Russian seizure of several Ukrainian ports and subsequent blockade of Ukrainian food exports compounded an already acute global food crisis further exacerbated by climate change, inflation, and supply chain havoc. Prior to the conflict, Ukraine had been the largest supplier of commodities to the World Food Program (WFP), which provides food assistance to vulnerable populations. In July, Russia and Ukraine signed an agreement to free more than twenty million tons of grain from Russian-controlled Ukrainian ports. The first grain shipments to leave Ukraine since the Russian invasion departed from Odesa on August 1, 2022; they arrived in Russian-allied Syria on August 15, although their originally presumed destination had been Lebanon. On October 29, Russia suspended the grain deal in response to an alleged Ukrainian attack on Russian naval forces, which Ukraine called a “false pretext.” Nonetheless, Russia did not enforce the blockade when Ukraine defiantly continued shipments, and Turkey quickly negotiated Russia’s return to the deal, which has been consistently extended to date.
In mid-August, the southern shift of the war’s frontline sparked international fears of a nuclear disaster at the Zaporizhzhia nuclear plant along the Dnipro River. The largest nuclear plant in Europe, the Zaporizhzhia facility was seized by Russian forces in the earliest stages of the war. Escalating tensions between the plant’s Ukrainian staff and its Russian occupiers have also raised uncertainty regarding its continued safe operation. Fighting in the territory surrounding the facility also raises concerns that the plant could be critically damaged in the crossfire: shelling of the plant’s switchyard has already led to a city-wide black-out in Enerhodar, where the plant is located. Representatives of the International Atomic Energy Agency (IAEA), including Director General Rafael Mariano Grossi, visited the plant in early September to assess the threat of a nuclear accident. In a report [PDF] on the findings of its inspection, the IAEA called for “a nuclear safety and security protection zone” around the plant and for “all military activity” in the adjacent territory to cease immediately.
In September 2022, Ukrainian forces made strong advances in the northeast and mounted a revitalized southern counteroffensive. Ukraine retook significant territory in the Kharkiv region, surprising Russian forces and cutting off important supply lines at Lyman before stalling and settling into a new front line. Shortly after, in southern Ukraine, Russia hastily withdrew across the Dnipro River as Ukrainian forces retook the city of Kherson and all territory west of the river. By the end of 2022, Ukraine had liberated half of its Russian-occupied territory, with 14 percent of the country remaining under Russian control.
Following the loss of Kherson, Russia redeployed forces eastward to Donetsk, in addition to sending tens of thousands of reinforcements to the area in advance of a February 2023 offensive. Russia also announced a partial mobilization on September 21, 2022, to refurbish the Russian army, prompting thousands of Russians to flee amid antiwar protests, and moved to annex four occupied territories: Luhansk, Donetsk, Kherson, and Zaporizhzhia. In his speech announcing the illegal annexation of Ukrainian territory, Putin also hinted at the possibility of nuclear escalation, claiming that the United States had set a precedent by dropping nuclear bombs on Hiroshima and Nagasaki during World War II.
The current conflict has severely strained U.S.-Russia relations and increased the risk of a wider European conflict. Tensions are likely to increase between Russia and neighboring NATO member countries that would likely involve the United States, due to alliance security commitments. The conflict will also have broader ramifications for future cooperation on critical issues like arms control; cybersecurity; nuclear nonproliferation; global economic stability; energy security; counterterrorism; and political solutions in Syria, Libya, and elsewhere. Additionally, Russia’s isolation has not only destabilized global energy and resource markets but also pushed the country to seek stronger strategic ties with those states (e.g., China) still willing to partner with it, largely in opposition to the West. The war has also compounded other global crises, with military operations and violence hindering the delivery and distribution of much-needed aid, including food, and exacerbating an already severe shortage of available global humanitarian assistance and resources.
Following a winter stalemate, Putin announced plans in February to take all of Donbas by March 2023 in an offensive surge. However, the attack made little progress and devolved into a months-long siege of Bakhmut, a town of limited strategic value with a pre-war population of seventy thousand. The United States estimates Russia suffered one hundred thousand casualties in Bakhmut, including twenty thousand deaths. Despite Russia’s low official numbers, Wagner Group boss Yevgeny Prigozhin concurred with U.S. estimates, adding that around half of those killed were Russian convicts recruited for battle. Ukraine also took heavy casualties in the urban warfare. By late May, Russia claimed to have taken the city, though Zelenskyy says his troops are still fighting there as Ukraine shifts to offensive actions.
On June 6, 2023, a breach in the Nova Kakhovka dam, sixty kilometers north of Kherson on the Dnipro River, caused severe flooding in southwest Ukraine, affecting over eighty thousand people who live in the riparian zone. Ukraine accuses Russia of blowing up the dam to prevent a southeastern offensive, while Russia claims Ukraine carried out the attack to deprive Crimea of water and distract from the battlefront. The Ukrainian dam operator says it has been destroyed beyond repair. Furthermore, the draining of the reservoir raises concerns over the availability of water to cool the Zaporizhzhia nuclear plant reactors, though the cooling ponds are reportedly stable.
In June 2023, Ukraine launched a much-anticipated counteroffensive, attempting to break through Russian defenses eastward in Donetsk province, including around Bakhmut, and southward in Zaporizhzhia province, which forms the “land corridor” to Crimea. Zelenskyy said Ukraine aims to liberate 18 percent of occupied territory in the current phase, but Ukrainian forces have met stiff resistance and suffered heavy losses against hardened Russian defensive positions, air superiority, and minefields. Nonetheless, Ukraine has made small gains on the ground and has stepped up attacks on bridges to Crimea, Russian ships, and buildings in Moscow.
Since February 24, 2022, the United States has committed nearly forty billion dollars in security assistance to Ukraine, including nineteen billion in immediate military aid and sixteen billion in humanitarian aid. Additionally, in early 2023 the Biden administration approved the provision of increasingly advanced weaponry, such as the Patriot air defense system, crucial for defending against Russian airstrikes, and top-tier battle tanks. The United States has also dramatically increased U.S. troop presence in Europe, bringing the total to more than one hundred thousand. On June 8, 2023, in a joint press conference with British Prime Minister Rishi Sunak, Biden said he believes the United States has the funds to “support Ukraine as long as it takes.” A day later, the Department of Defense announced another 2.1 billion dollars in military aid. While the United Nations, Group of Seven member states, EU, and others continue to condemn Russia’s actions and support Ukrainian forces, Russia has turned to countries like North Korea and Iran for intelligence and military equipment and continues to sell discounted oil and gas to India and China, among others.
By June 2023, the UN Human Rights Office recorded nearly nine thousand civilian deaths and over fifteen thousand civilian injuries since Russia’s full-scale military invasion of Ukraine on February 24, 2022. The violence has internally displaced nearly six million people and forced nearly eight million to flee to neighboring countries, including Moldova and Poland, a NATO country where the United States and other allies are helping to accommodate the influx of refugees.
On June 23, Putin faced a major internal challenge when Yevgeniy Prigozhin released a video claiming the Russian Ministry of Defense (MoD) shelled Wagner forces and announced a “march of justice” to unseat the military leadership. The mutiny follows months of tensions with the MoD, which Prigozhin often insulted and accused of not supplying adequate munitions, and an attempt by the MoD to reign in Wagner fighters. Wagner forces quickly occupied Rostov-on-Don and seized Russia’s southern military headquarters. Wagner convoys then advanced more than halfway to Moscow; Putin declared the march “treason” and offered amnesty for soldiers who stopped. On June 24, Belarussian President Alexander Lukashenko negotiated for Wagner soldiers to return to their bases and for Prigozhin to move to Belarus. Prigozhin’s true aims remain unknown, but the incident left both the Wagner Group and Putin weakened.
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