The attack that killed Iran's Supreme Leader Ayatollah Ali Khamenei came not in the middle of the night, as might have been expected, but in the middle of the morning.
That was because the US and Israel decided to take advantage of a piece of crucial intelligence that had arrived hours before.
For months, they had been watching for a moment of opportunity when senior Iranian figures might be meeting and they learnt Khamenei was going to be at a compound in central Tehran on Saturday morning.
They also had a fix on the location of other senior military and intelligence figures meeting at the same time.
For months the US and Israel had been tracking the supreme leader's movements. The exact methods they used are secret although US President Donald Trump in a social media post did hint at them.
"He was unable to avoid our intelligence and highly sophisticated tracking systems."
This could have been a human source reporting back but it may be more likely to be technical tracking of Iranian individuals.
In this case the intelligence, the New York Times says, external, came from the CIA but was passed on to Israel to carry out the actual strike.
The signs are that there is a division of labour with Israel focusing on strikes to hit leadership targets and the US more on military targets.
Crucially the intelligence provided enough forward notice of the supreme leader's movements and those of other officials to be able to plan an attack using jets which could fire long-range missiles.
Rather than a single decapitation strike, the plan was for this attack to signal the launch of a wider campaign and it was moved forward to take advantage of the window of opportunity.
www.bbc.co.uk/news/articles/c86y5540vnno