ABC News February 22, 2023

Russia-Ukraine war: Key events in the year since Russia invaded Ukraine

WATCH: Russian invasion of Ukraine: A visual timeline of the war

Russian President Vladimir Putin announced on Feb. 21, 2022, that he had recognized two Russian-backed separatist areas in eastern Ukraine, Donetsk and Luhansk, as independent states.

Ukrainian President Volodymyr Zelenskyy followed the announcement by saying that Ukraine had cut diplomatic ties with Russia. Putin then gave a speech on Feb. 24, 2022, announcing he would launch a "special military operation" in Ukraine.

MORE: Russia-Ukraine live updates

Minutes after the announcement, explosions could be heard in Kyiv. What followed was a full-scale invasion of Ukraine, with thousands of troops crossing the country's borders.

Russia seizes a quarter of Ukraine

In the early days of the invasion, it seemed as though Russians forces would enter the capital, Kyiv, after reaching the edge of the city very quickly.

Sputnik via Reuters
Russia's President Vladimir Putin takes part in an event marking Gazprom's 30th anniversary, via video link at a residence outside Moscow, Russia Feb. 17, 2023.

Russia had planned to topple the Ukrainian government within days of the invasion, but Putin and other officials had underestimated the strength of Ukraine's resistance.

MORE: Video Russia-Ukraine Crisis: February 24, 2022

By March 19, Russian troops had seized about a quarter of Ukraine's territory.

Western countries respond

The U.S. and its allies announced a wave of sanctions and trade controls against Russia in response to the invasion, along with its recognition of Donetsk and Luhansk as "independent" states.

Omar Marques/Getty Images
In this before-and-after composite image, top image shows Women and children rest inside the sports hall of a primary school which has been converted to a refugee center, March 01, 2022 in Przemysl, Poland. Bottom photo shows students from the elementary school that operated as a refugee camp take part in a handball tournament, Feb. 17, 2023 in Przemysl, Poland.

Sanctions were placed on Russia's biggest banks, Russian elites and their families. The imposed sanctions restricted Russia's ability to raise funds by adding additional prohibitions related to new debt and equity of major Russian state-owned enterprises and large privately owned financial institutions.

MORE: What to know about economic sanctions and how they will affect Russia

A turning point

At the beginning of April, it became clear that Russia lacked the forces it needed to take over Kyiv.

Russian forces retreated and abandoned nearly all the territory they had taken in the north of the besieged capital. As Russian troops retreated, they left behind a trail of horrors, which many observers would call human rights abuses.

Top Image: Chris McGrath; Bottom image: Roman Pilipey / Getty Images
In this before-and-after composite image, top image shows a man pushing his bike through debris and destroyed Russian military vehicles on a street, April 06, 2022 in Bucha, Ukraine. And bottom image shows Cars drive on Vokzal'na Street, which was one of the most affected during the Russian occupation, Feb. 1, 2023 in Bucha, Ukraine.

Mass graves containing hundreds of murdered civilians were discovered in Bucha, a town outside Kyiv.

By late May, Russia was devastating Mariupol in the south, a city that became a symbol of Ukrainian resistance. After over three months of siege, Ukrainian troops were forced to surrender the city.

MORE: 'Sickening' atrocities in Bucha, nearly 70% of Russian troops near Kyiv have withdrawn: Pentagon update Day 40

US supplies long-range weapons

By June, after retreating from Kyiv, Russia switched its focus to capturing eastern Ukraine, including the Donbas region.

What followed was a grueling artillery war, with Russia using its technical advantage and firepower to grind forward as Ukraine was battling to hold the line. The U.S. in July began to supply Ukraine with long range missile launchers, including U.S.-made High Mobility Artillery Rocket Systems.

Alexandru Dobre/AP
HIMARS systems launch rockets during a joint French-US exercise at a firing range in Capu Midia, on the Black Sea shore, Romania, Thursday, Feb. 9, 2023.

Russia also began struggling with shortages of men and ammunitions, as Ukraine appeared to be taking control of the war.

MORE: As Biden aims to punish Russia on world stage, sanctions hurt at home

Another turning point

A crucial turning point came in September, when Ukraine launched a spectacular counteroffensive in the northeast near Kyiv, collapsing Russia's lines and liberated thousands of square miles of territory.

Top image: Chris McGrath; bottom image: Roman Pilipey/Getty Images
In this before-and-after composite image, top image shows people walk amid destruction as they evacuate from a contested frontline area between Bucha and Irpin, March 10, 2022 in Irpin, Ukraine. Bottom image shows a street scene, Feb. 7, 2023 in Irpin, Ukraine. Irpin, a town outside of Kyiv, was turned into a battlefield early in Russia's large-scale invasion of Ukraine, as Russian forces made a failed attempt at seizing the capital.

Some military analysts said the route Ukraine took put an end to Russia's ability to go on the offensive. Russia was fighting to just hold on to the areas it has already captured.

MORE: Video Ukraine widens counteroffensive

By the fall, faced with the risk of full defeat, Putin declared a partial mobilization calling up 300,000 men. He began making threats about striking Ukraine with nuclear weapons.

AP
Russian recruits take a train at a railway station in Prudboi, in Russia's Volgograd region, on Sept. 29, 2022. President Vladimir Putin announced a partial mobilization, the first since World War II, amid the war in Ukraine.

On Sept. 30, desperate to hold on to Russia's war gains, Putin declared that he had annexed four Ukrainian regions: Zaporizhia, Luhansk, Donetsk and Kherson. But Russia didn't at the time fully control any of them. It lost the capital of one within weeks of Putin's declaration.

The U.S. and other western allies announced another wave of sanctions in response.

MORE: US slaps new sanctions on Russia after Putin annexes parts of Ukraine

Ukraine liberates Kherson

In November Ukraine liberated Kherson, on of the regions Putin had annexed. Russian troops were forced to withdraw.

Bulent Kilic/AFP via Getty Images
In this file photo taken on November 13, 2022 a man hugs a Ukrainian soldier as local residents gather to celebrate the liberation of Kherson, amid Russia's invasion of Ukraine.

Ukrainian Foreign Minister Dmytro Kuleba met days later with U.S. Secretary of State Antony Blinken in Cambodia.

The success in Kherson "is a testament once again to the remarkable courage of the Ukrainian armed forces, the Ukrainian people, as well as the strong support that Ukraine has from countries around the world," including the U.S., Blinken said ahead of their talks.

Russia changes its strategy

By the fall, Russia appeared to shift its strategy as it launched a massive campaign to destroy Ukraine's energy infrastructure. Human rights groups would accuse Russia of attempting to freeze Ukrainians as winter approaches.

Gleb Garanich/Reuters
A view shows the Kharkiv TEC-5 thermal power plant after being hit by a Russian missile strike during an attack on Ukraine, Kharkiv, Ukraine, Sept. 11, 2022.

There were Russian barrages of cruise missiles and Iranian supplied kamikaze drones causing nationwide blackouts in Ukraine.

Ukraine continued throughout the winter to call on Western countries to provide it with better air defense and more weapons.

Top photo: Anastasia Vlasova; bottom photo: Roman Pilipey/Getty Images
In this before-and-after composite image, top image shows the site of a rocket explosion where a shopping mall used to be, March 23, 2022 in Kyiv, Ukraine. Bottom photo shows cars parked on a parking lot, next to a shopping mall, Feb. 18, 2023 in Kyiv, Ukraine.

By December, the war was focused on the eastern Ukrainian city of Bakhmut as Russia brought in thousands of troops into the battle.

First Russian gain in months

In January, Russia made its first gain in months, capturing the small town of Soledar.

Fabian Bimmer/Reuters
Kyiv Mayor Wladimir Klitschko, German Defence Minister Boris Pistorius and Ukrainian Ambassador to Germany Oleksii Makeiev visit a training site in Munster, Germany, Feb. 20, 2023.

U.S. President Joe Biden on Jan. 25 agreed to give Ukraine heavy tanks, clearing the way for Germany and other European allies to do the same for the first time.

At the one-year mark

As the first anniversary of the invasion approached, Biden arrived in Kyiv on an unannounced trip. He met with Zelenskyy and other high-ranking officials, before announcing an additional $500 million in aid.

Evan Vucci/AP
President Joe Biden walks with Ukrainian President Volodymyr Zelenskyy at St. Michael's Golden-Domed Cathedral on a surprise visit, Feb. 20, 2023, in Kyiv.

Putin the next day, on Feb. 21, 2023, announced during his state-of-the-union address in Moscow that he had suspended the key U.S.-Russia nuclear treaty, opening the possibility for new nuclear tests.

Ukraine has liberated nearly 30,000 square miles of its territory since the Russian invasion began. But Putin appears to be preparing Russia for a long war.