Several hundred troops are being sent to beef up security at the US’ southern border with Mexico, the Department of Defense said. It comes as a caravan of several thousand migrants makes it way north through Mexico, RT reported.

Defense Secretary James Mattis is expected to sign an order sending at least 800 troops to the border in anticipation of the caravan’s arrival, a government source told AP.

The news seems to deliver on President Trump’s repeated warnings that he would deploy the military to the border in some capacity, if Mexican authorities did not do enough to halt the caravan’s advance.

While the president and his predecessors have requested state governors to deploy the National Guard to the border before, as Trump did in April when a smaller migrant caravan tried to cross into the US, he had warned last weekend that he would send in “the military, not the guard.”

Departing crime- and poverty-stricken Honduras two weeks ago, the caravan swelled in number as it approached the US, with the UN estimating it to be 7,000 strong last week. Since crossing into Mexico almost a week ago, the caravan has advanced north to the town of Mapastepec. Authorities there reckon that many of the 7,000 have dropped off, and that the caravan now numbers between 4,000 and 5,000 people.

Mapastepec is still over 1,000 miles from the US, a journey of several weeks for the remaining members. Some of the drop-offs have taken another route to the US, others have stayed in Mexico, and more have turned and gone home, some falling ill and some fearing attacks and harassment by criminals.