The independent journal +972 explains the impetus for the Great Return March:
Inevitably, among the 30,000 or so reported to have marched, there were young men who threw stones. That's what young males who want to demonstrate they are becoming grown men do. Israeli troops, overwhelmingly well armed with modern weaponry and subject to no apparent restraints when it comes to Palestinian lives, took the bait. It is very unlikely the killing is over.
Buzz Feed is accompanying a column of some 1000 Central Americans who are making their way across Mexico toward the US border.
The Washington Post has published a good background piece about the refugee caravan.
El Salvador, Guatemala, and Honduras are among the most violent countries in the world. Drug traffickers and gangs, some like MS-13 in El Salvador which originated in the United States, extort, rape and murder vulnerable people. Honduras has been particularly murderous to its own citizens ever since a 2009 coup in which the army removed the elected president. The Obama administration, under the leadership of then-Secretary of State Hillary Clinton, refused to join international condemnations of that coup and approved the successor government which has detained many opponents.
President Trump has seized on the approach of the refugee column to inflame fears of arriving migrants among his always anxious base in a series of his trademark incoherent tweets about "big flows". The head of the Border Patrol Union seems to be champing at the bit to repel what he sees as an invasion.
Trump's bluster about the approaching refugees is all the more ominous since last month a federal court essentially allowed US cops to shoot people on the Mexican side of the border without penalty.