NATO military officials are backtracking on the Secretary General's announcement earlier this week that 300,000 troops would be put on high alert across the alliance. They now say the number is a "concept" that the alliance aims to have in place by mid-2023.

NATO chief Jens Stoltenberg said on Monday that the alliance would increase the strength of the high-readiness force to more than 300,000.

This announcement implies a sevenfold increase from the 40,000 NATO troops currently on high alert. Two NATO officials told CNN that the number took defense chiefs of many NATO countries by surprise.

For example, it was not clear to them which troops from each Member State would be required to participate in this new high readiness force. It was a moment of obvious confusion and disunity in a well-orchestrated display of Allied unity.

Two senior NATO officials told reporters at a briefing that the new high readiness model will eventually replace the NATO Response Force model, but that it is still under development.

Officials have noted that under the new model, many troops will remain in their home countries rather than come under NATO Allied Operations Command. But they will be quickly available to NATO if a security crisis arises, for example if Russia attacks a member country.

Asked what would be the impetus for putting these forces on high alert under NATO command, one official said only that it would include signs and warnings of a potential attack.