[StormEye]

Why is Russia doing this to Ukraine?
What are the Russians trying to accomplish
with this action?

[AFreeBird]

Putin wants to put the band back together.

[Jmouse007]

Because the Russians want to steal and illegally annex and subjugate the sovereign nation of Ukraine. That’s why.

[pepsi_junkie]

The Ukraine hosts what has historically been one of Russia's only warm water ports. That is, the only port they have that doesn't ice up for significant portions of the year. They ceded it to Ukraine when the USSR collapsed but on condition of a 20 year lease. Since that lease expired the Russians have been concerned about losing access to that port, and taking steps to ensure they don't. With power in Ukraine shifting away from pro-Russian view, this became urgent to them. The port in question is their only way of controlling the Black Sea and projecting power and commerce throughout the Mediterranean. It is, in their view, essential and they will never willingly walk away from it.

That's what all their adventures in Ukraine are about.

[billakay]

What are they trying to accomplish? Defense of their territory!

These Ukranian ships made a run for the brand-new Crimean bridge while completely disregarding all protocols regarding notification to the controlling authorities of the strait.

If you or I were in charge of the defensive force in the area, we most likely would have made the same decision. Compound this with the fact that the "President" of Ukraine immediately declared martial law after this incident, which allows him to cancel the upcoming election (where he was polling ~10%).