President Trump saluted a Blackhawk helicopter hovering over the Rio Grande on Thursday, seeking to highlight the need for $5.7 billion for his trademark border wall to stop what he calls an “invasion.”

Next to the president stood a Customs and Border Protection officer and a Border Patrol agent. Both were working unpaid during the partial government shutdown, which on Friday tied the record for the longest in U.S. history.

Among the roughly 800,000 federal employees who’ve gone without pay in the three weeks since the shutdown began are tens of thousands of Border Patrol agents, Customs and Border Protection officers, immigration judges and Coast Guard crews — the workers on the front lines of the border security problems that the White House and Congress have been fighting over.