Defense Secretary Pete Hegseth and Thomas D. Homan, President Trump’s border czar, toured areas near Mexico. By Reyes Mata III and Eric Schmitt Reyes Mata III reported from the southwestern U.S.

Lt. Col. Phillip Mason stood on a narrow peninsula in early April just west of downtown San Diego, overlooking the coastal border between the U.S. and Mexico as a seasonal fog obscured the view. Mason ...