At 6.20 p.m. on 14 June, a migrant-advocacy group in Arizona tweeted: ‘URGENT: Border Patrol agents have surrounded and are actively surveilling the No More Deaths humanitarian aid camp.’ The camp was raided the next day by around thirty armed agents with fifteen trucks, two quad bikes and a helicopter.

For the past 13 years, No More Deaths, a ministry of the Unitarian Universalist Church of Tucson, has provided aid to undocumented migrants trying to cross the Sonoran Desert on foot. Part of its work is to leave caches of food and water along established routes. The camp near the small community of Arivaca, 11 miles north of the border, operates as a kind of humanitarian forward operating base.

In the raid, four Mexican men who had been receiving treatment for dehydration were arrested and charged with immigration violations. Agents had been watching the camp for two days while waiting for a warrant, having tracked the men for 18 miles. ‘The heavy presence of law enforcement,’ No More Deaths said after the raid, ‘has deterred people from accessing critical humanitarian assistance.’ As Jim Marx, a veteran volunteer with the organisation, puts it, ‘We’re just sitting ducks out there.’ In 2013, No More Deaths received written assurance from Border Patrol that the camp would be treated as a medical facility under the International Red Cross Code of Conduct, the first principle of which is that ‘the humanitarian imperative comes first.’

If the raid is symptomatic of a hardening of the border since Trump’s inauguration, it is also consistent with a well-established approach to US border control, which conscripts geography as an instrument of deterrence. In the mid-1990s, surveillance of crossing points near built-up areas was intensified, pushing migrants into more ‘hostile’, isolated regions, where they were less likely to be caught but far more likely to die. ‘The overarching goal of the strategy,’ a congressional report from the time reads, ‘is to make it so difficult and so costly to enter this country illegally that fewer individuals even try.’

Since the start of this year, in Arizona alone, more than 60 undocumented migrants are known to have died attempting to enter the US.