What is the migrant caravan?

The migrant caravan was formed late last week in San Pedro Sula, a city in northern Honduras known for high levels of violence. It originally numbered fewer than 200 people. But as word spread, the mobilisation quickly grew. By the time the group had crossed the border into Guatemala, its members travelling by foot and vehicle, it had ballooned to more than 1,000.

More migrants have joined this week — by some estimates it now numbers an extraordinary 4,000 people.

No group has claimed responsibility for organising this week’s caravan.

Why does it matter so much to Trump?

Trump made the fight against illegal immigration a central plank in his presidential platform, vowing to obtain tougher immigration legislation and build a border wall. But he has been unable to secure financing to build the wall.

With midterm elections only weeks away, he has renewed these attacks, warning of criminals pouring over the border to threaten American citizens and suggesting that unauthorised immigrants will cause job loss.

What will happen next?

The Mexican immigration authorities have said that migrants with valid documents and visas will be allowed in, but that those who attempt to enter illegally will be detained and deported. Those seeking asylum or some other forms of protection can request it, but will have to wait in a detention centre for as many as 45 days.

Secretary of State Michael Pompeo travelled to Panama City on Thursday to meet with President Juan Carlos Varela. He plans then to head to Mexico, where he is scheduled to meet on Friday with President Enrique Pena Nieto, among other officials. Migration, and the caravan, will surely be among the top issues on the agenda in Mexico City.