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José Antonio Kast's fortified frontier project combines trenches, electrified fencing and military deployment, but unauthorised crossings had already fallen by more than half before he took office.
Five days after taking office, Chilean president José Antonio Kast stood before heavy machinery in the Atacama desert and watched excavators break ground on what he called a new era of national sovereignty. The site was Chacalluta, the main land crossing between Arica and the Peruvian city of Tacna, and the work underway, three-metre-deep trenches cut into the earth by the Chilean Army's Corps of Military Labour, was the opening act of his administration's most visible policy: the Plan Escudo Fronterizo.
"This is not just a trench, it is much more, it is a system," Kast told reporters. "We want to use excavators to build a sovereign Chile, a Chile that has been violated by illegal immigration, by drug trafficking, by organised crime."
The figures complicate that framing. According to Chile's National Migration Service, unauthorised crossings through the northern border peaked at roughly 56,000 in 2021 and had already fallen to 26,275 by 2025, a decline of more than half, before Kast's policies came into effect. The country also remains, by regional standards, among the safest in Latin America, and no conclusive link has been established between migration and the rise in vehicle theft, kidnapping and homicide that Kast cited on the campaign trail.
What the numbers cannot fully capture is the political logic of the project. Migration had become, as Alejandro Mejía, professor of political science at Peru's Universidad Nacional Mayor de San Marcos, told La República, "the cornerstone of the campaign that brought Kast to the presidency." The wall is as much a communication strategy as a security one.
The plan envisions a layered architecture extending over more than 520 kilometres, from Chacalluta in the north to the crossing at Colchane near the Bolivian border. Initial works are concentrated near boundary markers 1 and 15 on the Peru frontier, skirting the formal Chacalluta crossing and a rail line. Official transit points will remain open.
Beyond the trenches, the design calls for walls and fencing of up to five metres, electrified perimeter barriers, thermal surveillance towers, radar systems and autonomous drones equipped with facial recognition. Military and police units are to maintain a permanent presence along the full length. Interior Minister Claudio Alvarado, who travelled north with Kast, set a 90-day benchmark: "Chile should be able to see the results of this border control work within the next three months."
Financing is being drawn from internal state resources, specifically the Army's budget and the Ministry of Public Works, without open public tender or private contractors. The total cost has not been disclosed. The speed of this approach facilitates deployment but limits scrutiny, particularly if the project expands to its proposed scale.
Legally, the government moved in parallel with the construction. In his first days at the Palacio de La Moneda, Kast signed decrees appointing a retired vice-admiral as presidential commissioner for the entire northern zone, expanding military authority in border areas and tightening migration law. Legislation submitted to Congress proposes reclassifying unauthorised entry as a criminal offence rather than an administrative violation, and restricting social benefits for irregular migrants.
The most legally sensitive aspect of the project may not be the wall itself but its location. Miguel Ángel Porras, an international law specialist at Lima-based firm Ugaz Zegarra, told Infobae that construction near the so-called Triángulo Terrestre, a 3.7-hectare coastal strip that remains a live point of contention despite the 1929 Treaty of Lima governing the broader land boundary, could be read as unilateral demarcation.
"There is no legal impediment for a country to erect physical barriers on its territory to protect its border," Porras said. "However, if the wall is built in disputed areas, especially near the Triángulo Terrestre, it can be interpreted as a unilateral demarcation act and strain international relations." In that scenario, he noted, Peru retains the right to bring a fresh case before the International Court of Justice in The Hague, the same tribunal that resolved the two countries' maritime boundary dispute in 2014 but left the terrestrial limit contested.
The Peruvian government has so far kept its response measured. Foreign Minister Hugo de Zela said Lima respects Chilean sovereignty and was monitoring the works for any impact on national security and human rights. He noted that Chile was acting within its own territory and that the barrier could, in one reading, reduce irregular entries into Peru as well. Peru has nevertheless reinforced police and military presence in Tacna and declared a state of emergency in the region. Former prime minister Denisse Miralles warned that Peru would not hesitate to take its own measures if territorial integrity were compromised.
On the central question of whether the wall will work, expert opinion is sceptical. Porras pointed to the US-Mexico barrier, the Spanish enclaves of Ceuta and Melilla, and Israel's fencing as evidence that physical barriers redirect rather than reduce migration flows, pushing routes into more remote and dangerous terrain while raising the cost and risk for migrants. "These measures are showy and do not stop the flow of migrants," he said. "It is a populist measure that seeks to show immediate results to the electorate, but it does not resolve the migratory phenomenon or the underlying security."
Porras also warned of an "embudo", or funnel, effect on the Peruvian side of the border, where migrants blocked from crossing into Chile could accumulate in vulnerable conditions and generate pressure on local authorities in Tacna. That concern has already prompted Lima to act: a binational migration cooperation committee, drawing in both foreign ministries and interior ministries, has been established to coordinate responses.
Economic ties between the Tacna-Arica corridor add a further complication. The area has long been bound by significant cross-border trade and tourism, and any disruption to mobility, even if aimed at irregular crossings, risks spillover effects on formal commercial activity. Mejía, the UNMSM political scientist, noted that the mutual economic dependence of the two northern cities is substantial, and called for the reactivation of the Chile-Peru Binational Cabinet, which has not met since 2022. "It is a vital space to place irregular migration as the principal bilateral agreement for short-term action," he said.
Kast, a seasoned right-wing politician who resoundingly won the December presidential runoff election, secured a 57% approval rating in the Cadem poll taken the weekend after the groundbreaking, suggesting the rapid deployment has resonated domestically. He has called on the entire political spectrum to support the border effort, including acknowledging the progress made by his left-wing predecessor Gabriel Boric, but not at the speed we estimated, he added. Defence Minister Fernando Barros Tocornal sought to reassure Lima that expulsions of irregular foreign nationals would not direct people toward Peruvian territory, framing the policy as consistent with good bilateral relations.
The deeper drivers of migration, economic instability and political crises in Venezuela and other countries of origin, remain beyond Chile's control. Whether the Plan Escudo Fronterizo narrows the flow further, pushes it elsewhere or simply photographs well at a groundbreaking ceremony may become clear within the 90-day window the government has set for itself.
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