Step 1: Nicaraguan Caltrop
These look like barbed wire barbs cut off and welded together, but they're much larger than any barbed wire I've seen. These were used in the revolution against Somoza in the late 70's. Nicaraguans threw them onto roads in front of troop truck convoys to delay them with flat tires.
Somoza was a ( yawn, yet another ) U.S. supported brutal dictator.
By the way, a recent issue of Time magazine reported that Nicaragua now has the lowest risk of terrorism in the hemisphere.