[WmDonovan]

Anyone know how border security was handled in WWII?

Nominally Mexico was on the allied side (a squadron of Mexican pilots did fight in the war, albeit trained and equipped by the US), but even so it (going through Mexico) would have seemed like an attractive way for German agents to slip into the US. Were there more agents then? A propensity to shoot first and ask questions later? Incidentally, there were some legendary gun slingers to come out of the Border Patrol in the first half of the 1900's(Charles Askins and Bill Jordan).

Anyone know what, if anything, was different then?

[kms61]

For one thing we had a very active counterintelligence operation south of the border, extending all the way from Mexico down to Brazil and Argentina. I had a history professor who was the acknowledged expert on this little known aspect of WWII.

[kms61]

And if I recall correctly, the job of the last remaining horse cavalry units in the US Army was patrolling the Mexican border.

[texastoo]

Anyone know how border security was handled in WWII

US citizens rode horses and secured the borders in this area. Old timers love to talk about this. They took turns day and night riding the border.