President Bush heads to New Mexico today to visit his new favorite school, the Border Patrol Academy. He wants it to train thousands more federal agents, but they'll make little difference unless Bush can teach Republicans the lesson learned by agents like Buck Brandemuehl a half century ago — the last time anyone could seriously claim the border was under control.

In the 1950's, federal agents were initially overwhelmed by waves of Mexican farmworkers illegally crossing the border. The number of immigrants apprehended surpassed half a million in 1951 and was approaching 900,000 in 1953, a level roughly comparable to the situation now.

Back then there were fewer than 2,000 federal agents patrolling the borders, less than a fifth the size of today's force. But within two years, the flow of illegal immigrants declined so drastically that the immigration service declared in its 1955 annual report, "The border has been secured."

And it stayed that way the rest of the decade. The number of immigrants caught kept dropping until it reached 45,000 in 1959 — a decline of 95 percent in just six years....

What stopped the farmworkers from sneaking across? It wasn't simply the get-tough measures that Republicans are calling for today. Although federal agents did intensify their efforts, conducting sweeps of farms and ranches, immigration officials realized that stricter enforcement wasn't enough.

Along with the crackdown, officials encouraged farmers and ranchers to legally hire Mexican temporary workers called braceros. As new rules made it easier to hire braceros, the number of these legal workers doubled to more than 400,000 at the same time illegal immigration was plummeting.

"We wanted people to come in the front door, not the back door," Brandemuehl says. The agents' job became simpler not only because there were fewer Mexicans to catch but also because there was more help from American employers. Once farmers and ranchers could legally get the workers they needed, they were more willing to cooperate with agents tracking down illegal immigrants.

Unfortunately, though, Congress started shutting the front door. The bracero program became controversial, partly because American labor unions objected to the competition and partly because of concerns that Mexicans were being exploited. Some of the complaints were legitimate, but Congress's response didn't leave immigrants any better off....