With his poll numbers tanking — his 36% approval is the lowest of his presidency — Joe Biden surprised no one by announcing a 90-day dispatch of 1,500 active-duty troops to the southern border in an attempt to show he’s getting tough on the flow of illegal migrants and fentanyl streaming into the country on his watch.

Thursday’s expiration of Title 42, the pandemic-era policy that granted Border Patrol agents greater authority to expel migrants for public-health reasons, will add thousands more migrants each day to the already-record totals.

But Biden’s troop-deployment gambit falls flat as a solution to the crisis. And it insults our troops by shunting them primarily to clerical and warehousing activities instead of the complex military maneuvers for which they are trained and where they could make the most difference.

I know because I was one of them — and I served on the border.