Ship to ship firing of mortars is obsolete. Of course it is available but that is not the primary purpose any more. There are all kinds of missions from the obvious to the covert. Obvious includes everything from denial of air space to shelling and launching of aircraft and missiles.
The covert, well….We know how the Russians like to screw with your internet. They will use ships to monitor and/or disrupt radio communications. I expect you will see a few brief (30 seconds or less), unexpected outages and wonder what happened. Busybodies will immediately Twitter and FB their friends complaining about it and Russia will know their jamming worked. They will also make a concerted effort to distribute back doors, keyloggers, trojans, sleepers, worms, etc. from local IPs. When they back off and head home, they’ll be ready for the next Crimea.
A ship is difficult to take down. They are networked with other ships, satellites, planes, etc. to sense and destroy threats from all directions. But, Russia has VA-111 Shkvals which are supercavitating torpedoes that blast through the water at speeds over 400km/h and are extremely difficult to detect and destroy. They can take down a well protected ship.
Shhh… NATO has even better stuff, and Russia knows it.
You won’t have to worry about an invasion or property damage. That would be too obvious for the power hungry despot. He will go the covert route. He has a ship load of unemployed hackers who studied hard in school but could not get jobs that would improve Russian industry through invention and productivity improvements. Instead he keeps them off the streets by teaching and encouraging hacking.
Be extra vigilant about your internet communications, computers, and passwords.
Got it?