Officials point to recent interceptions of vessels linked to a so-called "shadow fleet" and growing concern that Moscow is expanding weapon stockpiles and experimenting with cyber, economic and influence operations. Analysts say some scenarios under discussion would be almost unimaginable for European societies and could include nuclear options in extreme cases.
In response, NATO has stepped up exercises, especially in Germany, to test mobilization and defend the vulnerable Suwalki Gap — the narrow corridor between Poland and Lithuania that links the Baltic states to the rest of the alliance.