> US is the only country to have ever invoked article 5.

> https://en.wikipedia.org/wiki/North_Atlantic_Treaty

> Following the September 11 attacks, the Secretary General of NATO, George Robertson telephoned Colin Powell and said that declaring an Article 5 contingency would be a useful political statement for NATO to make. The United States indicated it had no interest in making such a request itself; however, it would not object to the council taking such action on its own.[55][56]