The Israelis have had outstanding success with this one:
“then put a 15’ fence on the Mexican side”
A friend took me to see the impressive steel border fence on the Mexican side. He said that after dark people set up ladders on both sides and charged for people to cross over. They were then picked up on the other side by people who drove them into California proper. We can’t see that with drones? (This was in 2009.)
Walls don’t work.
Walls with mines and claymores “work”.
Physical obstacles which are not supported by observation and direct fire, are just minor annoyances to an enemy.
There is no solution which does not involve the willingness for US forces to open fire on invaders.
A 35 foot physical barrier is very effective at stopping all but the most determined. And it makes even those much harder to see.
Walls are not 100%, but they are effective against the vast majority.
electrify them. they’ll work.
or a moat on the other side with some hungry florida crocs. or pirahnas.
The Israelis have had outstanding success with this one: