A whirring sound is heard in the sky above Niamey, the capital of Niger.
Several soldiers get into position. It’s a drill they’ve been through countless times.
As the engine noise grows louder, what at first appeared to be a small plane reveals itself as something else altogether.
It is a drone.
This is Base 101, an intelligence-gathering centre set up by the French military as part of Operation Barkhane.
Crucial role of drones
Launched in February 2014, its aim is to support countries in the region in their fight against Islamist extremists.
And drones play a crucial role, collecting information from the skies above the vast stretches of the Sahel and using their sophisticated cameras and radars to look down on a area roughly the size of western Europe.
The intelligence specialists in Base 101 are on the look-out for fighters belonging to groups like so-called Islamic State (IS) and al-Qaeda in the Islamic Mahgreb (AQIM).
The officer in charge of Operation Barkhane’s five drones is Lt Col Ben; for security reasons, the French military are now only referred to by their first names.
He opens the door of what looks like a metal container. Inside, there are two seats, several screens showing views from the air, a multitude of buttons and switches, flickering red lights and a couple of joysticks.
“This is where we pilot the drones,” he says. “We call this the cockpit.”
There are on average about 40 drone sorties every month; more than one a day. In this cramped and confined space, Lt Col Ben’s team work six-hour shifts, eyes glued to their screens.
Niger has now become a vital counter-terrorism partner for the West. A look at a map explains why.
The country is landlocked and surrounded by neighbours in a position to export the last thing Niger needs: instability.
To the north is Libya which, in recent times, has become a byword for chaos.
To the west lies Mali and its extremist uprisings.
Head east, and you reach Chad, struggling to contain its own internal tensions,.
The other major source of concern is on Niger’s southern flank, the Boko Haram insurgency in Nigeria.
Clashes there have sparked a human exodus. And more than 200,000 people have fled to Diffa in south-eastern Niger.
Traders hit hard
It’s a dusty run-down place just a few kilometres away from the Nigerian border.
Already living under the shadow of poverty and food insecurity, Diffa’s meagre resources are being stretched to the limit.
In the town’s main market, I meet Ousmane Oumara, a local English teacher.
“Traders here have been hard hit by developments across the border,” he tells me.
“Things aren’t like they used to be.”
Nearby, a grain merchant explains that the price of maize and millet keeps going up because supplies from Nigeria have been cut off.
“Sometimes I hear the sound of gunfire just outside the town and I’m afraid,” says Ousmane.
With so many people arriving from Nigeria, there is not enough shelter for them in Diffa itself.
So tens of thousands of refugees have had to make do as best they can, living in temporary encampments which line the Route Nationale 1 – Highway Number One – which runs parallel to the Nigerian border.
The unofficial frontier
At one of these temporary refugee villages, Assaga, people have separated along national lines. Along one one side of the road are straw shacks housing the displaced from Nigeria; on the other, similar fragile shelters are now home to those who have fled their homes in the border settlements of Niger.
As I arrive, pointing to the left, my driver tells me: “Here is Assaga-Nigeria.”
He then nods his head towards the other side, adding: “And there is Assaga-Niger.”
The road has become a sort of unofficial frontier.
I ask one young woman on the Niger side if she feels safe here.
“It’s more secure along the road than back in my village,” she answers. “I can’t go back home because I’m scared of Boko Haram.”
Her story is echoed all along a 200km (120 miles) stretch of road.
‘I have the answer!’
As he sits cross-legged inside a makeshift tent, to escape the sweltering heat of the midday sun, a 16-year-old boy explains his own personal tragedy.
For his own safety, he prefers we don’t use his real name. That’s because, while he and his family managed to escape the violence, his 14-year-old brother has been left behind.
“He was studying in Diffa and Boko Haram took him away. They forced him to join them.”
You can see in his eyes that he deeply misses his brother, but he’s also worried about what will become of him.
“They’re going to fill his head with all sorts of ideas I don’t like – and I want nothing to do with that.”
In another camp a little further along the road, some big white tarpaulin tents stand out.
From inside comes the sound of laughter and the eager shouts of children.
With their hands up, they’re all calling out: “Teacher! Teacher! I have the answer!”
The teacher is Mustafa Diri. When he was forced to escape his village, just 8km from the Nigerian border, he didn’t want to leave his school behind.
So he took it with him.