MADRID, Aug. 8 -- On August 15, five days from now, the next mass crossing attempt at Ceuta is scheduled - not by any official process, but by social media posts that Spanish intelligence services have been monitoring since early in the month. Spain's response is 300 riot police and 2,000 troops, positioned at the same border stretch where last month's surge overwhelmed every security measure in place and produced the largest single migration event in the enclave's recorded history.

The Interior Ministry told 20minutos newspaper on Saturday that it was ready for new incidents. The Defense Ministry confirmed that troops already garrisoned in Ceuta would remain in position until a formal decision to redeploy them was made. Neither ministry...