This comes in the wake of an increase in losses of SA-21 air defence systems in parts of Ukraine occupied by Russia, the UK defence ministry said in its latest Intelligence Update on the situation in Ukraine.
It added that "as its westernmost outpost and bordered on three sides by NATO member states," including Poland, Moscow views the Kaliningrad Oblast as one of its most strategically vulnerable regions.
The decision to move the systems "highlights the overstretch the war has caused for some of Russia’s key, modern capabilities," the assessment says.
Russia invaded Ukraine on February 24, 2022, launching the largest military campaign in Europe since World War II.
Sunday is day 641 of Russia’s war on Ukraine.
Source: IAR, gov.uk