Defence reviews come along quite regularly, mainly because governments struggle to fit their budgets to their ambitious commitments.
The UK tends to spend a bit on a lot of capabilities – at sea, in the air and on land, with an increasing effort in cyberspace.
In more than 30 years since the end of the Cold War, various governments have deployed the reduced defence spending dividend on other priorities, from tax cuts to the health service.
But this announcement marks a turning point. This spending review looks to be far more significant than any we have seen for decades.
For a start, ambitions seem to be getting narrower, focussed on the 'Euro Atlantic' area. That is a change from the last review's tilt towards being a power player in waters around Asia.
One of the Royal Navy's aircraft carriers is currently flying the flag in that arena, as tensions rise between China and Taiwan.