A line of Mexican National Guard and Army trucks rumbled along the border separating Ciudad Juárez and El Paso, Texas, Wednesday, among the first of 10,000 officers Mexico has sent to its northern frontier following tariff threats by President Donald Trump.

Masked and armed National Guard members picked through brush running along the border barrier on the outskirts of Ciudad Juárez, pulling out makeshift ladders and ropes tucked away in the trenches, and pulling them onto trucks. Patrols were also seen on other parts of the border near Tijuana.

It comes after a turbulent week along the border after Trump announced he would delay imposing crippling tariffs on Mexico for at least a month. In exchange, Mexican President Claudia Sheinbaum promised she would send the country’s National Guard to reinforce the border and crack down on fentanyl smuggling.

Trump has declared an emergency on the border, in terms of migration and drug trafficking..

The U.S. said it would, in turn, do more to stop American guns from being trafficked into Mexico to fuel cartel violence, which has rippled to other parts of the country as criminal groups fight to control the lucrative migrant smuggling industry.

On Tuesday, the first of those forces arrived in border cities, climbing out of government planes. Guard members in the Wednesday patrol confirmed that they were part of the new force.

At least 1,650 officers were expected to be sent to Ciudad Juárez, according to government figures, making it one of the biggest receivers of border reinforcements in the country, second only to Tijuana, where 1,949 personnel are slated to be sent.

During Secretary of State Marco Rubio’s trip through Latin America – where migration was at the top of the agenda - the top American diplomat thanked the Mexican government for the forces, according to a statement by the Mexican government.

The negotiation by Sheinbaum was viewed by observers as a bit of shrewd political maneuvering by the newly elected Mexican leader. Many had previously cast doubt that she’d be able to navigate Trump’s presidency as effectively as her predecessor and ally, former President Andres Manuel Lopez Obrador.