UK: Royal Navy Shadowed Russian Submarines for Weeks to Foil Cable Sabotage

That was a very clear violation though. Russia has never violated UK sovereign airspace: much like the submarines here they've always been caught on approach. They've been caught in areas that the UK does not consider meet the standard of a sovereign violation. This is an important distinction for a country like the UK that was a key founding member of the international legal framework that governs much of the interactions between states. It has a very strict set of rules of engagement and Russia hasn't yet met that bar to get an airplane shot down or - on this case - a torpedo fired at a submarine. I appreciate that this may seem a subtle (and possibly meaningless) distinction for some but the rules based international order is being tested by countries like Russia and only the US has managed to take the bait in a profound way so far. Even Iraq had a multi year process of getting a UN resolution (for example). The point being that there is a clearly defined process that allows time for belligerents to have a second thought and perhaps at least round the edges off warlike actions. It's important to the UK that this stays the case as its government believes it's at the nexus of the relative peace and stability that's defined the world since the 1940s. Losing sight of that is exactly what Russia is hoping for: a lawless planet where it can possibly carve out concessions from smaller nations (more likely in my opinion Russia gets its shit pushed in like on Ukraine but hey). There may well be a point where a line is actually crossed, and ironically perhaps it's the competence of the UK's armed forces that's meant these possibly legitimate (more likely bait) incursions by Russia have been interdicted every single time.

You mean like when we were in open war in Vietnam?