We should be wary, particularly with our closest friends and allies, of breaking down the trust and confidence that lie at the foundation of relationships.

Walls and barriers alone are insufficient to insure security.

If you build a 50-foot wall, you'll soon be confronted with a 51-foot ladder.

As former Homeland Security Secretary Janet Napolitano pointed out, if you build a 50-foot wall, you'll soon be confronted with a 51-foot ladder. You need a strategy that involves layered defense: deployed patrols, sophisticated sensor equipment, and surveillance from the air. That is what has had a positive impact over the last generation.

The work the Mexicans are doing in terms of migration control on Mexico's southern border is crucial to our own border security.

Not only are the numbers of migrants entering the United States at the lowest levels in a generation, but they are now largely Central American. Four out of five border-crossers detained in South Texas are Guatemalan, Honduran or Salvadoran. They are driven by violence and poverty in their home countries and the desire for family reunification.

Our security in a global world must be looked at on a continental basis.