France's drastic decision to recall its ambassadors to the United States and Australia marks one of the gravest rifts among allies in living memory.
And it will also be watched by rivals like China and Russia with glee.
The extraordinary diplomatic rebuke follows a decision by Canberra to ditch a French submarine contract for a new nuclear submarine partnership with Washington and London.
Yet the French fury - conveyed in a communique by the foreign minister - omitted any mention of Britain even though the UK is clearly also in the firing line.
Gerard Araud, a former French ambassador to the US, wrote on Twitter: "You can interpret the omission of the UK as a sign of conciliation or contempt. Your choice."
The French move dashes hopes on the UK, US and Australian side that normal relations with Paris would resume once French "disappointment" at losing out on the multi-billion pound submarine deal faded.
Their so-called AUKUS partnership was meant to be about bolstering the defences of democratic countries in the face of a growing challenge posed by authoritarian China in the Indo-Pacific and beyond.
But instead of strengthening western unity, it has triggered this significant rupture - an outcome that could well be exploited by Beijing and Moscow.
Any friction between western allies is an opportunity for their authoritarian rivals to amplify.
The US, UK and France are all members of the G7 group of industrialised, democratic powers and the NATO defence and security alliance, while Australia is also a close and like-minded ally.
Frantic efforts will be going on behind the scenes to try and defuse the row
However, President Emmanuel Macron, heading into an election year, has been badly bruised on the international stage and needs to hit back.
His country not only lost a big chunk of business when Australia sank the submarine contract, but it will also miss out on the prestige of providing the Australian navy with such a strategic asset over several decades.
Adding to the injury, Mr Macron will have to watch the US and the UK take France's place.
Not a great look for a president who sees his country as the predominant military power in Europe.
The anger was clear in foreign minister Jean-Yves Le Drian's statement: "The abandonment of the ocean-class submarine project… and the announcement of a new partnership with the United States… constitutes unacceptable behaviour between allies and partners".