Russian President Vladimir Putin's "special military operation" into neighboring Ukraine began on Feb. 24, with Russian forces invading from Belarus, to the north, and Russia, to the east. Ukrainian troops have offered "stiff resistance," according to U.S. officials.
The Russian military has since launched a full-scale ground offensive in eastern Ukraine's disputed Donbas region, capturing the strategic port city of Mariupol and securing a coastal corridor to the Moscow-annexed Crimean Peninsula.
A look at the two leaders at the center of the war in Ukraine and how they both rose to power, the difference in their leadership and what led to this moment in history.
Here's how the news is developing. All times Eastern.
Apr 08, 2022, 5:45 PM EDT
Claims Russia not involved in train attack 'unconvincing': Pentagon
During his daily press briefing, Pentagon spokesman John Kirby was clear that the U.S. believes that Russia was behind the rocket attack on a train station in eastern Ukraine earlier Friday.
"We find unconvincing Russian claims that they weren't involved, particularly when the ministry actually announced it and then when they saw reports of civilian casualties they decided to unannounce it,” Kirby said during Friday afternoon's briefing. "So our assessment is that this was a Russian strike and they used a short-range ballistic missile to conduct it."
Kirby called it a part of the trend by Russia of "brutality" and "carelessness" in not avoiding civilian casualties as they carry out this war in Ukraine.
At least 50 people, including five children, were killed in the rocket attack in Kramatorsk, Ukrainian authorities said.
A Kremlin spokesman denied involvement in the attack, saying Russia's Armed Forces do not use the type of missile used in the strike and that no combat tasks were planned in the region.
-ABC News' Luis Martinez
Apr 08, 2022, 3:23 PM EDT
EU president witnesses mass grave in Bucha
European Union President Ursula Von der Leyen was seen on camera witnessing a mass grave in Bucha, Ukraine, during a visit to the demolished city with the EU's chief diplomat Josep Borrell and Ukrainian Prime Minister Denys Shmyhal.
EU Commission President Ursula von der Leyen and EU High Representative for Foreign Affairs Josep Borrell (behind) and Denys Shmyhal (green cap), Prime Minister of Ukraine, stand next to body bags from a mass grave in Bucha, Ukraine, April 8, 2022.
Michael Fischer/Picture-Alliance via AP
After touring Bucha, Von der Leyen met with Ukrainian President Volodymyr Zelenskyy and handed him an envelope with a questionnaire, marking the first step toward membership in the EU. Zelenskyy said he'd have responses in one week.
Global officials have accused Russian troops of committing war crimes after graphic images emerged of civilians lying dead in the streets of Bucha following the withdrawal of Russian forces.
At a press conference Thursday Secretary of State Antony Blinken said, "The sickening images and accounts coming out of Bucha and other parts of Ukraine have only strengthened our collective resolve and unity."
Apr 08, 2022, 3:12 PM EDT
Russia has lost 15-20% of combat power, US says
The Pentagon is "not buying" Russia's denial of responsibility for the Ukraine train station attack that killed at least 50, a senior U.S. defense official said Friday.
"They originally claimed a successful strike and then only retracted it when there were reports of civilian casualties," the official said. "It's our full expectation that this was a Russian strike -- we believe they used a short-range ballistic missile, an SS-21."
As Russian troops retreat from some Ukrainian cities, some of the Russian battalion tactical groups (or BTGs, with roughly 800-1,000 troops each) that have withdrawn back across the Belarusian and Russian borders have been essentially "eradicated" from the fighting in Ukraine, according to the senior defense official.
A woman walks amid destroyed Russian tanks in Bucha, in the outskirts of Kyiv, Ukraine, April 3, 2022.
Rodrigo Abd/AP
"There's just nothing left of the BTG except a handful of troops and maybe a small number of vehicles," the official said.
In terms of total losses -- counting troops, tanks, aircraft and missile inventory -- Russia has lost between 15-20% of the combat power it originally had arrayed against Ukraine since the beginning of the invasion, according to the official.
People walk by an apartment building destroyed during fighting between Ukrainian and Russian forces in Borodyanka, Ukraine, April 5, 2022. Ukrainian President Volodymyr Zelenskyy accused Russian troops of gruesome atrocities in Ukraine and told the U.N. Security Council on Tuesday that those responsible should immediately be brought up on war crimes charges in front of a tribunal like the one set up at Nuremberg after World War II.
Vadim Ghirda/AP
According to the official, some of the withdrawn Russian forces are now making their way to the Russian cities of Belgorod and Valuyki, to the northwest of Donbas. But there are "no indications" that fresh troops are waiting there to join them, the official said.
For now, degraded Russian BTGs are "exploring the option of" consolidating, banding together remaining troops and supplies to form new units, the official said.
Russia is also aiming to recruit upwards of 60,000 new troops, according to the official.
After Russian BTGs rebuild, "the most likely course of action would be for them to move immediately south right into the Donbas," the official said.
The Pentagon now estimates more than 40 Russian BTGs are positioned in or near the Donbas region. The estimate was "more than 30" on Wednesday, meaning up to 10,000 more troops have arrived in recent days.
Five children were among those killed when Russian rockets struck the station in Kramatorsk in Donetsk Oblast on Friday morning, according to Ukraine's state-owned railway company. At least 100 people were injured, according to Donetsk Oblast Gov. Pavlo Kyrylenko.
A photo published on Ukrainian President Volodymyr Zelenskyy's Telegram channel, shows blood stains among bags and a baby carriage at the railway station in Kramatorsk, Ukraine, April 8, 2022.
Ukrainian President Zelenskyy's Telegram via AP
Russia has denied involvement in the attack, which occurred as "thousands" of civilians fleeing the Russian invasion were at the train station waiting to be taken to "safer regions of Ukraine," according to Kyrylenko.
"Civilians are killed when they stay in their homes, and they're killed when they try to leave," Porter said. "Actions like these demonstrate why Russia did not belong on the U.N. Human Rights Council, and they also reinforce the U.S. assessment that members of Russian forces are committing war crimes in Ukraine."
Porter declined to say if the department considers the train station attack a war crime, saying, "Assessing individual criminal liability in specific cases is the responsibility of courts, as well as other investigatory bodies. But as the secretary, Secretary [of State Antony] Blinken, has said, 'Those responsible for war crimes and other atrocities committed in Ukraine will be held to account.'"
