Turkey, Pakistan and Saudi Arabia have signed a mutual defence agreement that works on the same principle as NATO's Article 5. An attack on one of the three counts as an attack on all three. The agreement was signed on Friday and is called the Mecca Agreement on Joint Defence.

Turkish Foreign Minister Hakan Fidan immediately clarified what everyone was thinking. The pact is not aimed at Iran, he says. It is a general commitment to security support, not an alliance against any particular country.

Three Sunni states, worried about Iranian missile strikes on oil exporters in the Persian Gulf, sign a joint defence agreement - and then have to explain it has nothing to do with Iran. If the explanation was necessary, the answer is obvious.

Fidan says the aim is to strengthen joint deterrence against any act of aggression. He also announced that Erdoğan wants the alliance expanded, with Egypt mentioned as a possible candidate. Turkey claims it remains open to other countries in the region, but that this does not replace existing alliances.

And here is the detail worth holding on to. Fidan recalled that NATO has 32 countries, while these are, as he put it, very modest but concrete steps - and that they took two years and eight months.

Why this concerns us

Turkey is a NATO member. That same Turkey now also has a second defence obligation, signed with a country that possesses nuclear weapons and with the world's largest oil exporter. The agreement provides for a ministerial committee modelled on NATO, headquartered in Saudi Arabia. Operational details will be settled at the first session.

So the structure exists before the content does. That is the classic move of someone who wants the framework ready for the moment they need it.

The Balkans have long practice in reading moves like this. A country that is in one alliance and signs a second rarely does so because the first one is working beautifully. Erdoğan has spent years testing NATO's patience - from Russian missile systems to vetoes on enlargement.

Is Ankara building a fallback plan, or just exercising leverage over its allies? We will know the answer the first time something actually happens and Turkey has to choose which phone to pick up.