Early on Sept 19, Azerbaijan's president set in motion a lightning-fast military plan months in the making that would redraw the geopolitical map and avenge an ignominious defeat suffered by his father some 30 years ago.
President Ilham Aliyev had often spoken of returning the mountainous Nagorno-Karabakh enclave to Azerbaijan's control after its ethnic Armenian inhabitants broke from Baku's rule in early 1990s.
Now, a confluence of factors had convinced Aliyev, 61, that the time was right, Elin Suleymanov, Azerbaijan's ambassador to Britain, told Reuters.
"The stars aligned for certain reasons and President Aliyev saw the alignment," said Suleymanov, including the inability or unwillingness of Russia, the West, or Armenia to intervene.
Two senior officials and a source who has worked with Aliyev underscored that the decision to take back the breakaway region took shape over months as diplomatic realities shifted.
It was also deeply personal for the president, they said.
"President Aliyev is completing something that his father could not do because he ran out of time," said one of the sources.
In three interviews before and after the military operation, Aliyev's foreign policy adviser, Hikmet Hajiyev, said Baku's patience with the status quo had snapped. It could not accept what he called a "grey zone" with Karabakh's own armed security forces, which he likened to the mafia, on Azerbaijani territory.
The Karabakh defence force has since disbanded under the terms of a new ceasefire deal.
Hajiyev said Azerbaijan gave the Russians "minutes' notice" before the operation began.
Nikol Pashinyan, Armenian prime minister, did not heed calls from opposition politicians to intervene, saying his country needed to be "free of conflict" for the sake of its own independence.
The West, which had previously tried to mediate, merely urged Aliyev to halt his operation and was duly ignored.
With Russia distracted in Ukraine, Aliyev appeared to sense a window of opportunity.
In December last year, Azerbaijani citizens describing themselves as environmentalists unhappy about illegal mining began to block the Lachin corridor, the only road linking Karabakh to Armenia. Reluctant to risk escalation, armed Russian peacekeepers did not act. Baku ignored calls from Washington and Moscow to unblock the road, citing a weapons-smuggling risk.
In May, in an attempt to advance peace negotiations, Pashinyan made what looked like a breakthrough offer: Armenia was ready to recognise Karabakh as part of Azerbaijan if Baku guaranteed the security of its ethnic Armenian population. The source who has worked with Aliyev called the shift "very important".
Karabakh slipped from Azerbaijan's grasp in the chaos that followed the Soviet Union's break-up. In a 1988-1994 war, around 30,000 people were killed and more than one million displaced, over half Azerbaijanis.
Aliyev's father, then president Heydar Aliyev, was forced to agree to a ceasefire that cemented Armenia's victory.
Ilham, who had succeeded Heydar on his death in 2003, signed an oil deal with a BP-led consortium a year later that gave Azerbaijan funds to start building a modern army.
For years, Moscow's alliance and defence pact with Armenia, where it has military facilities, deterred Baku from using force even as Russia sold weapons to both sides.
But Moscow's ties with Armenia began to sour in 2018 when Pashinyan, a former journalist, led street protests that brought him to power at the expense of a long line of pro-Russian Armenian leaders.
And as Azerbaijan's army overhaul and modernisation drive intensified, Armenia limped from crisis to crisis.
Then Russia's full-scale invasion of Ukraine in February 2022 changed the equation again, drawing Moscow into a war of attrition with Kyiv.
On the morning of Tuesday, Sept 19, residents of Stepanakert, Karabakh's capital and known as Khankendi by Azerbaijan, heard loud and repeated artillery fire.
Aliyev's anti-terrorism operation had begun, with ground forces backed by drones and artillery sweeping in to overwhelm Karabakh's defensive lines.
Within 24 hours, Baku declared victory and the Karabakh Armenian fighters agreed to a ceasefire that obliged them to disarm.
"Azerbaijan regained its sovereignty at around 1pm yesterday," Aliyev told the nation.
For Azerbaijan, Karabakh's return paves the way for tens of thousands of Azerbaijanis who once fled it to go back, a promise Aliyev's father gave repeatedly.
"President Aliyev has delivered the testament of his father," said Suleymanov.
* The writer is from Reuters news agency