Venezuela has been butting heads with its neighbor, Colombia, since August — tensions punctuated by Venezuelan military exercises along their shared border.

The US is working with Colombia and others to isolate and remove Venezuela's embattled president, who is backed by Russia.

Moscow's and Washington's outreach in the region has a military dimension, with Russian maintaining Venezuela's weapons and the US offering to sell some its latest hardware to Colombia.

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Tensions have simmered between Venezuela and its neighbors, Colombia in particular, for months as a US-led international effort tries to isolate and remove embattled Venezuelan President Nicolas Maduro.

Venezuela-Colombia relations have been fraught for nearly two decades, and their 1,300-mile border has been closed for long stretches during that period. But the latest tensions have an international dimension, with the US and Russia backing different sides as part of a broader competition for influence.

Colombia has received millions of Venezuelans who have left their country since 2015, and President Ivan Duque has taken a hard line against Maduro.

A former FARC commander known as alias Ivan Marquez reads a statement that ex-FARC fighters will resume their insurgency, in an undated screen grab from a video released, August 29, 2019. FORMER FARC DISSIDENCE HANDOUT via REUTERS

One of Duque's main issues, Colombian criminal and rebels groups operating in Venezuela, became more heated at the end of August, when former members of the FARC rebel group released a video, which appeared to have been filmed in Venezuela, announcing a return to arms three years after signing a peace deal with Duque's predecessor.

Colombia has presented evidence of Colombian armed groups active in Venezuela (though photos Duque presented at the UN in September were actually taken in Colombia), but that isn't a controversial allegation, according to Geoff Ramsey, assistant director for Venezuela at the human-rights advocacy group Washington Office on Latin America.

"I think the more controversial element of Duque's claims is that Venezuela is a state sponsor of terror and that there is overt cooperation between the Maduro government and armed groups in Colombia," Ramsey said. "The trickiest thing to prove is to what extent is the Maduro government itself coordinating actions with Colombian guerrillas, and that's difficult to prove in part because of the complete break down of law and order in Venezuela."

Colombia has stuck to its assertions. At the end of August, Foreign Minister Carlos Holmes Trujillo said there was "no doubt" it would be easier to fight those groups if Maduro were gone.

A special alert

A military vehicle carrying missiles during a military exercise at Garcia Hevia airport in La Fria, Tachira state, September 10, 2019. SCHNEYDER MENDOZA/AFP/Getty Images

Those tensions increased in September, when Maduro said military exercises would take place along the border and ordered the armed forces to be alert for a potential attack by Colombia.

The exercises kicked off on September 10. Remigio Ceballos, the Venezuelan military's Strategic Operational Commander, said 150,000 troops and police were conducting activities "related to security ... and the interception of any invasion."

Along with the soldiers, armored vehicles, and aircraft Venezuela deployed for the exercises were mobile rocket launchers and anti-aircraft systems, among them the Russian-made S-300, considered the most advanced air-defense system in Latin America.

Trujillo called the drills "a threat" reflecting "the consistent bad actions of a [Maduro] government which creates crisis situations."

A senior military commander said on September 11 that Colombia's forces were "on a special alert" in response to the exercises. "We have been openly threatened," the commander said.

National Guard members during in a military exercise at Garcia Hevia airport in La Fria, Tachira state, September 10, 2019. SCHNEYDER MENDOZA/AFP/Getty Images

"Maduro and his cronies, they've always had an annual exercise regime, so part of this is the annual regime just continuing," US Navy Adm. Craig Faller, head of US Southern Command, said at a Defense Writers Group breakfast in early October, when asked about those exercises, which ended on September 28.

Maduro's government is "spending money on moving their forces around to make a statement to the neighbors," Faller said, calling Maduro "an illegitimate leader" propped up by Russia, Cuba, and, to a lesser extent, China.

"Some of it's [Maduro's] attempt to show that he's still capable and has military forces," Faller added. "We always are concerned about a nation's military. I would never discount or discredit somebody's forces as being incapable. That's not the right approach for planning."

Venezuelan National Guard members during a military exercise at Garcia Hevia airport in La Fria, Tachira state, September 10, 2019. SCHNEYDER MENDOZA/AFP/Getty Images

The US will "look at what [Venezuelans] have or what they could have, and we work through that continuously and share that assessment with our partners," Faller said. "So we're monitoring that and sharing information on that, and it also gives us an indication of the readiness of those forces."

Faller didn't elaborate on that readiness, but in an email, US Southern Command said Venezuela's "security capabilities continue to decline steadily."

Venezuela's "inability to address pressing internal security challenges and continued desertions indicate low levels of operational readiness and professionalism," it added. "Transnational criminal and narco-terrorist groups operate virtually unchallenged inside Venezuela, vividly demonstrating the security force's current ineffectiveness."

'A threat to the region'

A woman with a rocket launcher during military drills in Caracas, August 26, 2017. Carlos Becerra/Anadolu Agency/Getty Images

Venezuela's military has been strained in 2019. Hundreds of members have defected this year, and discontent is widespread among those who remain, particularly lower-ranking troops.

"The Venezuelan military has definitely shown a fraying at the edges," Ramsey said. "But I've also been surprised at their cohesiveness. I think there was an expectation in January that this whole thing was just going to fall apart."

Late President Hugo Chavez and his successor, Maduro, have cultivated loyalty and punished dissent in the ranks, which has helped keep Maduro in power despite deepening disdain for his government.

"There's definitely been a breakdown in terms of professionalism, resources [and] chain of command ... but I don't think it's necessarily a 'Mad Max' scenario ... they have functioning equipment, [and] they have a military structure in place that goes beyond the formal standing army," Ramsey said, referring to militias and other armed groups backing Maduro.

Russian-made Venezuelan air force Sukhoi Su-30MKV multirole strike fighters fly over a military parade for Venezuela's 206th independence anniversary, in Caracas, July 5, 2017. FEDERICO PARRA/AFP/Getty Images

The functioning of that equipment, like those S-300s, is owed largely to Russian support, including repeated deployments of technicians to Venezuela, including a contingent that arrived on September 25.

"There are hundreds of Russians in Venezuela," and Venezuela has "a significant amount of Russian arms ... and Russian support to maintaining [and] upgrading those arms," Faller said. "That's a primary line of effort for Russia."

Those technicians, like Maduro's meetings with Russian President Vladimir Putin and the deployment of Russian bombers to Venezuela in December, have taken the current tensions beyond a regional dispute.

"There's no denying that Venezuela's crisis has been increasingly shaped by broader geopolitical trends," Ramsey said. "Russia is definitely deepening its foothold in Venezuela, both through oil contracts as well as military contracts."

Those military contracts include Russian Su-30 fighter jets, 24 of which Venezuela ordered in 2006 and now operates alongside US-made F-16 fighters acquired earlier. (At least two Su-30s have been lost in fatal crashes, including one this month.)

Colombian air force personnel do maintenance checks on a Kfir fighter jet in Barranquilla, July 17, 2019. US Air Force/Tech. Sgt. Danny Rangel

Those Russian jets are "a threat to the region," Maj. Gen. Andrew Croft, head of Air Forces Southern, told Foreign Policy earlier this year.

That's part of the reason the US has offered to sell Colombia 15 of the latest version of the F-16, according to Foreign Policy. Those jets would be "a great advancement" for Colombia's "capability to defend their sovereign air space," Croft said at the time.

In addition to a commercial victory, the US would benefit from that sale by offsetting support Maduro has gotten from Russia and China, Sergio Guzman, director of advisory firm Colombia Risk Analysis, wrote in a note in late August.

But for now Colombia seems unlikely to go for the sale, Guzmán told Business Insider. Bogotá has been restrained and has sought to build a case against Venezuela internationally. Budgetary restrictions and a lack of public support for major defense expenditures also make that purchase less likely.

"Colombia will always be interested in that hardware," Guzmán said, "but it will be difficult to justify from a fiscal point of view in the current juncture."

A deal for Maduro

A Colombian security forces member guard on the Simon Bolivar international bridge in Cucuta, as people cross the border with Venezuelan, June 9, 2019. REUTERS/Carlos Eduardo Ramirez

Venezuela's military exercises have concluded, but tensions in the region remain elevated, and there's still a chance an incident along the border could escalate, especially given command-and-control issues among Venezuela's armed forces and the panoply of armed groups and illicit activity going on there.

Florida Sen. Marco Rubio, an influential adviser on Latin America to President Donald Trump, said this month that no one in the region has requested US military action and that he wouldn't support it, echoing the US envoy to Venezuela.

Duque and Brazilian President Jair Bolsonaro, who has also taken a hardline on Venezuela, have both also rejected military intervention.

Venezuelan President Nicolas Maduro and Russian President Vladimir Putin. Maxim Shemetov/Reuters

China and Russia, knowing Maduro has few options other than threatening conflict, are also likely urging restraint, Guzman said.

Moscow may even be open to a new arrangement in Venezuela if it can hang on to investments it already has there.

"Russia, I'm convinced, is out to make the United States look bad at every turn of the corner and hang on to some of their traditional alliances," Faller said.

"I think ultimately Putin is interested in providing a nuisance for the United States in its own hemisphere, but I suspect he's not particularly married to Maduro," Ramsey said.