Speaking of overt acts of war, Russia just blew up a merchant vessel in EU territorial waters. A little blockade will do just fine.
Russia, on the other hand, together with the Syrian government bombed so many hospitals in Syria that Doctors Without Borders stopped reporting the locations of their hospitals.
https://www.theguardian.com/world/2016/feb/18/msf-will-not-s...
https://www.hrw.org/news/2020/10/15/syria/russia-strategy-ta...