Along the Chari and Logone rivers separating Cameroon from Chad's capital, four flat-bottomed boats, mounted with machine guns, brimming with Chadian and other special forces, round the curve as they approach the riverbank.
Forming an assault force, heavily armed soldiers leap out of the vessels and race up a slope to take up positions while backup forces have their machine guns at the ready.
It's all part of a military exercise that simulates going after a high-value target – a leader from the ISIS-affiliated Boko Haram insurgency, who's taken up residence in a huddle of huts on the far side of the riverfront, a terrorist safe haven. The assault force demonstrates crucial military steps before capturing and eliminating him.
Three weeks of U.S.-led counterterrorism exercises, known as Flintlock 2017, ended last month in Chad, which, along with surrounding countries, has been targeted in deadly violence by Boko Haram. The Flintlock exercises take place each year in a different African country.
Boko Haram's 8-year-old uprising began in northeastern Nigeria, to the west of Chad, and has spilled over its borders, killing thousands of people and driving almost 3 million from their homes across the region. The war left a humanitarian catastrophe in its wake.
The Trump administration's budget blueprint pledges to boost U.S. military spending by 10 percent — but also promises deep cuts in foreign aid. It's not yet clear what that might mean for U.S. counterterrorism efforts here or elsewhere in Africa, though the White House has boosted the U.S. military's authority to carry out strikes in Somalia against al-Shabaab militants linked to al-Qaida.
At the same time, the U.S. — the biggest donor to the United Nations — is making the case for cuts in U.N. funding and wants to see changes in U.N. peacekeeping operations, most of which take place in Africa.
"We need to show results," U.N. Ambassador Nikki Haley said earlier this month. "We need to find value."
Support for foreign nations' counterterrorism efforts, as opposed to big American deployments, were a key tool of the Obama administration. Last year, the U.S. gave $156 million for military support, training and border security in the region straddling Nigeria, Niger, Chad and Cameroon, known as the Lake Chad Basin. The military officer in charge of Flintlock 2017, Brig. Gen. Donald Bolduc, has called this region "Ground Zero" when it comes to fighting extremism in Africa.
Bolduc, the Special Operations commander in Africa, says for now, the U.S. military is continuing to pursue its objectives.
But the prospect of aid cuts worries many, as the region's humanitarian situation risks deteriorating. The U.N. warns there is a risk of famine in Nigeria's northeast, exacerbating a humanitarian disaster that has already seen children, especially those under the age of 5, dying of malnutrition, hunger and starvation.
The U.S. has given more than $321 million since last year to help those in the Lake Chad Basin, including more than $175 million in emergency food aid.
"Our assistance to this area is critical for promoting stability," said Matt Nims of the U.S. Agency for International Development, speaking at a House subcommittee hearing earlier this month.
'The military can't do it by itself'
U.S. special operations troops don't typically deploy in large numbers to help African security forces work together and fight Boko Haram, but local officials say they're useful in serving as the glue that helps everything stick together. For Flintlock 2017, forces from 27 countries took part at seven training sites across west and central Africa.
"Chad, Cameroon, Nigeria, Niger – unfortunately, the entire region, we are facing the same reality," said Cameroonian police commander Gilbert Nagassou, in charge of the border post at Kousseri, just across the river separating Chad and Cameroon. "That's why we must join forces and together confront terrorism."
When it comes to fighting Boko Haram's threats to the Lake Chad Basin, "The military can't do it by itself," Bolduc told NPR in Ndjamena, Chad's capital. "Regionalize all the efforts, work closely together in an effective military construct ... and then bring in the police, the civil administration, religious leaders and include anybody working to bring the stability necessary to the local villages."
A U.S. special forces commander involved in Flintlock, who asked that his name be withheld for security reasons, says the challenges shouldn't be underestimated.
"We have a regional issue of Boko Haram, [which] easily exploits the seams between international boundaries – especially when you have something like a river way that separates two nations," he says. "And they currently use islands in this pretty broad [Chari and Logone] river to hide out in. It's an easy area to have ungoverned and hard to police and patrol."
Members of U.S. military and, for the first time, law enforcement agencies are working with African security forces to enhance their techniques, said Billy Alfano, a special agent with the State Department's law enforcement arm, the Bureau of Diplomatic Security. "Interoperability" – groups and forces working well together — is the current buzzword.
"It's critical for our African partner nations to work together and more and more important for police to collaborate with the military, to conduct joint investigations and to truly counter the terrorism threat in the region, with law enforcement in those communities," Alfano said.
Law enforcement agents are often first responders after an attack, he explained, so training them in forensics and skills like fingerprinting also helps "attack the terrorist network."
Alfano said this year's more broadly focused exercises reflected an emphasis on governance and rule of law, "making a transition from a military-controlled area to training the police to more effectively take over when the military has moved on."
And there was what he called "a mass migration training," to teach rural communities how to respond to potential terrorists who may cross porous borders where large numbers of people are already traveling.
During Flintlock, training scenarios involved agents from across the region simulating the aftermath of a terrorist bombing, as well as chasing and apprehending hostage-taking terrorist suspects.
"Terrorism knows no boundaries or borders," warned Nagassou, the Cameroonian police commander. Deadly Boko Haram bomb blasts and suicide bombing raids have targeted all four countries battling the terrorist network, he said.
"Boko Haram has pledged allegiance to Islamic State," he said, "so geographic frontiers mean nothing to this group or other terrorist networks and their regional allies. Borders are simply a joke to them — they have connections and communications."
Terrorists, he said, easily slip across.
"If there's intelligence from Nigeria and it's relayed to Chad, then Cameroon must also be made aware," said Nagassou. "And Niger also needs to be informed, so that together we can nip Boko Haram's nefarious plans in the bud and stop them attacking our people."
Battle-hardened Chadian special forces are already familiar with this problem. For the past few years, they've been taking on Boko Haram extremists since violence spread across the border from northeastern Nigeria. They also were a critical force that helped end the occupation of northern Mali by al-Qaida-linked extremist fighters in 2013.
"Chadian military history has demonstrated our experience and know-how. It's not today that the Chadian army is learning how to capture and destroy the enemy. Chadian forces are used to pursuing Boko Haram," said Lt. Col. Brahim Mahamat Dahab, Chad's chief of staff for the Flintlock 2017 exercises.
He says the river scenario assault force exercise shows that Chad is capable of working with Americans, Italians "and the military from any given country, as well as our neighbors, reinforcing capacity. That's what we want to demonstrate. We need to share that knowledge with others who are also fighting Boko Haram," Brahim told NPR passionately.
Back on the banks of the Chari-Logone river in the Chadian capital, the assault force exercise ends and the Boko Haram leader is captured. Amid a hail of protective gunfire, the special operations forces head back down toward the boats and speed off down the river. Mission accomplished.
For this raid, a textbook success: the same way they hope a real-life operation would end. With the exercise over, the group whoops with satisfaction and relief.