Donald Trump has thrown a new idea into the Ukraine negotiations - "closing the skies" over Ukrainian territory as a security guarantee. And, as often happens with his proposals, the reaction was more careful than the headline suggests. From the Kremlin, spokesman Dmitry Peskov admitted this was something new: "There were no such statements before. No one previously considered the question of closing the skies."

It sounds like a concession to Kyiv, but the devil is in the details. "Closing the skies" in practice means NATO armed forces operating over Ukrainian territory - and that, as Peskov immediately stressed, is directly contrary to what Moscow cites as its goal in the war. In other words, the proposal that looks like a road to peace on paper is, for Russia, precisely the thing it says it started the war over.

Here it is worth stopping to ask - what is Trump actually offering, and what is he just saying out loud? The no-fly zone idea is not new in the world of diplomacy; it is among the most dangerous tools that exist, because someone has to enforce it, and enforcement means planes and missiles ready to fire. The Balkans remember this well from the nineties - a "no-fly zone" is not a peaceful phrase, but a military operation under another name.

Whether this is a serious proposal or another balloon floated to see how all sides react is hard to say until Washington itself clarifies what exactly it means. For now we have a statement from Trump, a cautious answer from Moscow, and all of Europe reading between the lines. And in a war that has gone on for years, every new word is measured not by how it sounds, but by who will have to enforce it.