SAN DIEGO — The typically quiet stretches of communication on a Border Patrol scanner have recently been marked by extended periods of silence, interspersed with reports of monitoring a single migrant for several hours. This radio chatter evokes a sense of nostalgia for earlier times before 2017, when the United States became a leading destination for asylum-seekers.

“One pair is situated way down there; we’ll see if they start to come up,” one agent noted.

“Perhaps they’ll try moving north soon,” another agent replied.

In a declaration that refers to “America’s sovereignty” facing threats, former President Donald Trump announced a border emergency, coinciding with a time of relative stability following years of considerable unrest. On Thursday, active-duty military personnel arrived in San Diego and El Paso, Texas, as part of an initial deployment involving 1,500 troops.

Reports indicate that arrests related to illegal border crossings have seen a dramatic decline of over 80%, dropping to approximately 47,000 in December from a record high of 250,000 during the same month the previous year. This notable decrease began when Mexican authorities ramped up enforcement within their borders about a year ago and continued to decline after President Joe Biden implemented stringent asylum restrictions in June.

For Trump, Biden’s measures fell short of what was necessary. The latest figures on border arrests during Biden’s administration showed numbers close to a 4.5-year low, significantly lower than the figures from much of 2019 in Trump’s first term, yet nearly three times higher than April 2017, which was a focal point for Trump at his campaign rallies.

The Border Patrol spent six hours accompanying agents in San Diego, identified as the busiest area for illegal crossings over the last year, and did not encounter any migrants until the last half-hour of this observation. Three men from China and one from Malaysia voluntarily surrendered to agents moments after crossing through a gap in the border wall. Concurrently, eight individuals from India and one from Nepal crossed and awaited assistance. These individuals were then transferred to processing facilities located in white tents that were established during Biden’s presidency.

It remains uncertain what the subsequent steps are for these individuals. One major obstacle for Trump’s administration is the significant expense and diplomatic difficulty associated with deporting individuals back to distant countries. For instance, Venezuela and Nicaragua, which are among the U.S.’s adversaries, do not cooperate in accepting their citizens back, while Cuba restricts flight options.

The responsibilities of Border Patrol agents have shifted considerably in recent months, moving away from the rapid processing and release of asylum-seekers with immigration court appearance notices. Agents are now returning to their more traditional role of tracking individuals and small groups who are attempting to avoid capture.

Many agents expressed frustration during Biden’s tenure as arrests surged above 2 million for two consecutive years, although the pace slowed sharply just before Trump resumed office. In December, fewer than 7,000 migrants were released into the U.S., a staggering 96% drop from nearly 192,000 the previous year. In El Paso, only 211 were released in the third week of January compared to over 10,000 a week in December 2023.

In Thursday’s activities in San Diego, agents concentrated on an area characterized by challenging mountain trails offering a wide view of Tijuana, Mexico, and the urban layout of San Diego. Migrants attempting to avoid apprehension often navigate through these landscapes for up to two days before reaching vehicles operated by smugglers. Agents stationed in strategic locations monitor their movements and strategize their own responses.

“Can anyone see them? You can’t miss them,” one agent communicated over the radio.

“Potentially two so far,” another agent replied.

Almost a year ago, agents were faced with large numbers of asylum-seekers voluntarily surrendering, many of whom had to endure harsh temperatures as they waited for several days, drawing the scrutiny of judicial authorities regarding the exposure of children to extreme conditions. At times, hundreds congregated near border walls in San Diego, where volunteers provided essential supplies like bandages, juice, and sandwiches through openings in the barrier.

In remote mountainous areas east of San Diego, sizable groups crossed over nightly, many hailing from China and South America. Within a short time, these asylum-seekers found themselves dropped at bus stops in San Diego.

Karen Parker, an advocate providing support and medical care to migrants in the mountains, treating injuries such as broken bones and cuts, reported a significant decrease in the number of individuals she encountered — down from 600 to 800 per night a year ago to mainly smaller groups now. She noted that on occasion, larger groups of about 40 still appear.

Parker remarked on the stark change since Trump took office, calling it “a dead standstill,” possibly influenced by adverse weather conditions like freezing temperatures and wildfires.

She observed more individuals being picked up in vehicles, signaling an uptick in potential smuggling activities, as opposed to last year when migrants typically awaited apprehension and subsequent release with court notices.

In the last week of Biden’s presidency, arrests in the San Diego sector dwindled to an average of 236 per day from a peak of over 1,400 daily in April. The arrest count on Wednesday stood at 136.

Trump’s directives will largely depend on how to finance detention and transportation, as well as how to negotiate with countries that refuse to repatriate their citizens. In his first term, he had utilized emergency authorities to reallocate billions from the Defense Department for border wall construction.

“To safeguard the security and safety of U.S. citizens, to defend the States against invasion, and uphold my duty to ensure the laws are faithfully executed, it is my responsibility as President to decisively prevent the illegal entry of individuals at the southern border,” Trump stated during his emergency declaration on Monday.

In Arizona, Pima County announced the closure of two migrant shelters in Tucson due to the federal government’s halt in releasing migrants to these facilities. Since 2019, the county provided shelter for over 518,000 individuals.

Jewish Family Service of San Diego reported that its shelter has not seen any new arrivals since the Trump administration discontinued the use of the online border app, CBP One, for legal migrant entry. Prior to this, the shelter assisted 791 individuals the week before Trump was inaugurated.