UK and France agree on a historic upgrade to their military alliance and announce coordination of their nuclear deterrent capabilities.

• In previous posts, we have analyzed shifts in Europe's strategic defense posture: a significant change is now unfolding openly, marking a pivotal moment for European nuclear deterrence.

• Britain and France have, for the first time, explicitly agreed to coordinate their independent nuclear arsenals—a historic development captured in the newly signed Northwood Declaration.

• Here is a key quote: ‘‘we do not see situations arising in which the vital interests of either France or the United Kingdom could be threatened without the vital interest of the other also being threatened.’’

• Notice the deliberate emphasis on the word "interests" vs imminent threat to national security or even just national security.

• This is an extremely wide application of nuclear cooperation.

• In other words, this means that if Britain has some faraway island that it deems of high strategic value being under threat, France will agree to accept it as a mutual threat.

• So, for example, if an RAF base in Cyprus was under threat by, say, a Russian submarine, France would consider that as a mutual threat.

• In other words, this nuclear cooperation isn't only about immediate big-ticket items—like imminent national security threats to the main territories of France and the UK, respectively.

• As such, this is a monumental shift.

• And how did we arrive here?