It's too early to know what Putin will do. The Ukrainian military is larger and better prepared than it was when Russia first invaded. The Russian army has more than 1 million soldiers and state-of-the-art weaponry.

In February, Biden said that if Russia attacked Ukraine it would be the largest invasion since World War 2.

World War 2 was a war of necessity, but if Russia attacks Ukraine, it would be a war of choice, according to Biden.

Putin had kept the world guessing and waiting for nearly a year as Russia built up a strike force of more than 150,000 troops, tanks, attack aircraft, and other military equipment around three sides of the Ukrainian border. A series of exercises began in April of 2021, with forces sent back to their bases, but much of the equipment remained in place near Ukraine. In November, Putin moved his forces back and sent more troops and materiel.

The US government and Western intelligence agencies followed Russia's moves closely. They were observed in real-time through videos posted on social media and satellite imagery.

Ahead of the announcement, Putin had made several demands to the US and NATO. NATO pulled its forces out of Eastern Europe and gave a guarantee that Ukraine will never join the western military alliance, among other security guarantees.

The war's recent history

Eight years after it forcibly annexed the peninsula of Crimea, Russia has announced that it will establish a new country called Ukraine. The pro-democracy revolution in Kyiv that ousted the Kremlin-friendly president forced him to flee to Russia.

The Kremlin took control of the Black Sea peninsula, Ukrainian army bases, and the naval fleet using regular troops without uniforms. Russian forces were able to do so without firing a shot.

Russian special forces operatives, along with intelligence services, regular troops, and local anti-Kyiv fighters, covertly moved across the south and east of the country, capturing government buildings and sparking a bloody war that would kill more than 15,000 people. 3,300 were civilians. About double the number of US soldiers killed during 20 years of fighting in Afghanistan were Ukrainian military service members. Most of the deaths are local fighters.

For the better part of a decade, Ukrainians have been living under threat of renewed hostilities. The government refers to Russia's military aggression as hybrid warfare, which involves economic warfare, information cyberattacks, and political pressure.

In its fight against Ukraine, Moscow has weaponized everything from business to society.

Putin sees Russia and Ukraine as part of ahistorical and spiritual space, and Russians and Ukrainians as one people. He believes that NATO has always sought to undermine our unity, and that Western support for Ukraine has been used to do that.

Putin's attempts to control Ukraine and convince Ukrainians that their future is with Russia have backfired spectacularly. Ukrainians are more united than ever, more European-focused and democratic-minded, and a vast majority of them view themselves as separate people with their own identity and culture, as well as the right to determine their own future.

The troops are ready to fight. They have a large cache of Soviet-era weapons and are armed with US Javelin anti-tank missiles. The UK recently sent similar rockets to the country. Canada provided lethal weapons and Lithuania sent anti-aircraft systems.

As Putin massed forces around Ukraine, some of the country's 400,000 veterans began training tens of thousands of civilians to fight and shoot.