German-made Leopard tanks from Warsaw arrived in Ukraine as Polish Prime Minister Mateusz Morawiecki visited Kyiv to send a "clear and measurable signal of further support".
More Polish tanks will be sent soon, Morawiecki said, also offering to train Ukrainian pilots to fly F-16 fighters, as Western allies underlined their unwavering support.
As the war entered its second year, Zelenskyy pledged to do everything to defeat the invaders in the coming months.
"We endured. We were not defeated. And we will do everything to gain victory this year," Zelensky said in a statement.
Ukrainian Defense Minister Oleksiy Reznikov said his army was gearing up for a counteroffensive.
"We are working hard to prepare and secure it," he said.
- 'Spirit is strong' -
On the frontline in eastern Ukraine, Kyiv troops' morale remained high.
"God is helping us. Nobody thought that Ukraine would hold," said a soldier who goes by the call sign "Cook".
"I know that miracles happen," said the soldier from the 95th Separate Air Assault Brigade in the eastern region of Donetsk.
Despite military setbacks and sanctions, Putin, 70, has refused to back down, accusing the West of supporting neo-Nazi forces and claiming Russia's survival was at stake.
"We are protecting people's lives, our native home," Putin said in his state of the nation address on Tuesday. "And the goal of the West is endless power."
Putin's assault on Ukraine and mobilization of reservists have sparked what might be Russia's largest mass exodus since the Bolshevik Revolution in 1917.
With television propaganda in overdrive, many Russians have rallied behind Putin despite economic trouble and multiplying casualties.
"The country is really changing for the better," said Lyubov Yudina, a 48-year-old security guard in Moscow.
But Ruslan Melnikov, a 28-year-old teacher, was dejected. "I don't see any future now," he said.
A year ago to the day, Russian President Vladimir Putin stunned the world by sending troops across the border, a move seen as punishment for Kyiv's pivot to the West.
The year-long war has devastated swathes of Ukraine, displaced millions, turned Russia into a pariah in the West and, according to Western sources, caused more than 150,000 casualties on each side.
Protests against Moscow's aggression were planned across Europe to mark the invasion anniversary.
In Berlin, activists placed a bombed-out Russian tank in front of the Russian embassy.
Crowds fell silent for a minute from Tallinn to London while key buildings across Europe were draped or lit up in the blue and yellow colors of the Ukrainian flag.
A year ago, Russian troops sought to rapidly install a pro-Moscow regime in Ukraine but failed to conquer Kyiv and subsequently suffered defeats in northeastern and southern Ukraine.
Since October, Russia has pummeled Ukraine's energy infrastructure, causing power shortages that have left millions in the cold and dark.
In a recent Ukrainian poll, nearly one in five said they had lost a loved one in the war.
But despite the daily trials, Ukrainians said they refused to be cowed.
In Bucha, where Russia has been accused of widespread atrocities, 64-year-old Galyna Gamulets recalled coming under fire from Russian troops for "more than two weeks."
She voiced pride in her nation and said that "we will succeed" in repelling the invaders.
"Thanks to aid from Western countries, we will win because our spirit is strong, said Yuriy Lototskyi, a 60-year-old electrician, also from Bucha.
"We just need help with the weapons."
As the tanks arrived, the West, which has imposed increasingly stringent sanctions on Russia and boosted humanitarian aid and arms supplies for Ukraine, unveiled more help on Friday.
The United States, which has been leading efforts to bolster Kyiv militarily, announced sweeping sanctions not only aimed at Russia but also hitting "over 200 individuals and entities" across Europe, Asia and the Middle East that are supporting Moscow's war.
The new aid package from Washington came days after President Joe Biden arrived in Kyiv on a historic visit and pledged new arms deliveries.
On Thursday, the United Nations voted overwhelmingly to demand Russia "immediately" and "unconditionally" withdraw its troops from Ukraine.
But key players China and India abstained, as fears rose in the West that Beijing was considering arming Russia.
Releasing a 12-point position paper on Friday, Beijing urged Ukraine and Russia to hold peace talks as soon as possible.
Western allies were cautious in their reception of the call, with German President Frank-Walter Steinmeier saying it was "still doubtful" if Beijing sincerely wanted to play a constructive role in seeking peace.
NATO chief Jens Stoltenberg said Beijing simply "doesn't have much credibility because they have not been able to condemn the illegal invasion of Ukraine."