The Pentagon is deploying 5,200 troops to the Southwest border in an extraordinary military operation a week before nationwide elections in which President Donald Trump wants voters to focus on what he calls an “invasion” — a slow-moving caravan of Central American migrants, AP reported.

The number of troops being sent is more than double the 2,000 who are in Syria fighting the Islamic State group.

Two caravans of migrants, traveling mostly on foot, are still hundreds of miles from the U.S. border with Mexico. Most are poor, carrying the belongings that fit into a knapsack and fleeing gang violence or poverty. And any who complete the long trek to the border already face major hurdles to asylum in the country — both physical and bureaucratic — to being allowed to remain in the United States.

Trump, eager to keep voters trained on immigration in the lead-up to the midterm elections, stepped up his dire warnings about the caravans, tweeting, “This is an invasion of our Country and our Military is waiting for you!”