Obviously, a complicated subject but I'll try to summarize as best I can:

## tl;dr

Putin is trying to create a symbol to the Russian people of the strength and unity of the Russian people as things get worse in the global economy.

While at the same time he's trying to get more secure borders as Russia becomes weaker due to its demographic problems.

## Slightly longer explanation

- Putin feels like Ukraine is part of Russia, similar to how China feels about Taiwan but with much more historical backing. (see note 1).

- Ukraine almost joined the EU and when the president stopped it the US and EU supported revolts in the country that saw him ousted from power. Imagine if Russia and Canada almost joined in a union together and when Trudeau vetoed it Russia ran an intelligence operation that saw him removed from office. The US would probably be pretty nervous about what's going on in their border.

- Russia's population demographic situation means that they are likely to see widespread societal collapse in the next ~20 years if they don't do anything. (see note 2).

- Russia's current geography is indefensible if the West wants to attack it since Ukraine is essentially the front door to Moscow.

- Covid, internal struggles, and tensions between the US and China mean that the focus of the US is elsewhere.

- Putin likely sees Biden as the president least likely to have a strong response to aggression.

- Contrary to popular opinion the winter is when you want to attack in eastern Europe (it's the spring and the fall that kills you).

- Crimea is a warm water seaport which is viewed as an important economic and military asset for Russia, but Ukraine has been cutting off their water supplies since the initial invasion 6 years ago.

## Notes

1 - Why some people might claim Russia is part of Ukraine:

Both Russia and Ukraine started their history in the same place: the historical Kievan/Rus nation. In which the Vikings rules over the local Slavic population.

However, this nation collapsed into fighting princelings and then was combined into two board regions: the western portion was absorbed by Poland/Lithuania while the eastern section was conquered by the Mongols.

This split was right down the middle of modern Ukraine.

The Mongols ruled over their lands brutally - pushing everyone into poverty, tearing down their preexisting identity, and setting up an authoritarian government structure.

In turn the people in this region developed a culture of unbelieve stoicism, unity, and grit in order to survive the Mongols.

While those under Lithuania were heavily influenced by European Catholicism during the same time.

When it was eventually reunited Ukraine became the bridge between these two worlds. In the west, half in the east.

For the next several hundred years Ukraine was both part of Russia but also occasionally rebelling if they ever drifted too close to them.

2 - Why Russia's demographics mean they're screwed

Look up the Russian population pyramid.

Basically, birth rates declined throughout the Soviet Union's history, except for a slight bump during the perestroika era.

This, combined with shortening lifespans in Russia has led to population loss in the 00s before that brief perestrokia boom echo'ed and Russia's population froze in place for the 10s.

Now we're at a peak.

Russia will see their population halve in the next few decades.

And the only people having large numbers of children in Russia right now are their Muslim minority groups.

This means the ethnic Slavs are feeling in a very real way their culture being displaced.