One everyone knew about that could not be played off as an accident or one small unit that got carried away. Read war histories, large conflicts often start out with a succession of small scale feints, probes, and black operations.

> One everyone knew about that could not be played off as an accident or one small unit that got carried away.

Poisoning people in Britain was pretty obvious. But there have been so many others.

Any attack during which the country attacked invokes article 5. Czechs didn't, and I'm not surprised.

Similarly Russia launched a cruise missile back in 2023 that flied over half of Poland and crashed in forest near Bydgoszcz. Poland did not invoked article 5, even if it could be justified.

Reason is similar in both cases:

- war is a BIG DEAL, it would likely cause flight of foreign investment and other businesses

- if NATO helps it would be an easy win, but there would still be loses in the region

- it's possible many countries in NATO don't see that as a sufficient justification for the war, which might cause problems in NATO and reduce the security guarantees for when they are REALLY needed (i.e. if Russia invades somebody in region for real)

TL; DR: it's not worth it for the attacked country, even if Russia is long past the point of "deserving it"