Senate negotiators have struck upon an ingenious plan to make immigration reform palatable to conservatives: They are building a Maginot Line along the southern border.

Republican Senators John Hoeven of North Dakota and Bob Corker of Tennessee yesterday announced their plan for a $3.2-billion “border surge." ABCNews.com reported:

The money would be spent on everything from observation towers, fixed cameras, drones, helicopters and planes, mobile surveillance systems, seismic detectors and ground radar.

It also calls for 700 miles of new fencing added to the 42 miles already in place, as well as 20,000 new border patrol agents, double the current number.

Senator Lindsey Graham, Republican of South Carolina, said the plan includes enough manpower to put a border-control agent every 1,000 feet.

France built its Maginot Line -- named for a French minister of war -- in the 1930s along its border with Germany. Like the border fortifications envisioned by Hoeven and Corker, the Maginot Line was supposed to be unpassable. Also, like the U.S. Senate's border surge, it provided an excellent talking point for right-wingers. Why mobilize against the Nazi threat, French fascists asked, when the Maginot Line is there to protect the homeland?

Of course, Germany invaded France via Belgium, a route that German generals had plotted a mere 35 years earlier -- well before the Maginot Line existed.

Immigrants wishing to enter the U.S. illegally after the southern border is fully militarized will probably opt for a similar strategy. Already, an estimated 40 percent of illegal immigrants invade the U.S. not across the Rio Grande but via international airports. Then they overstay their visas. It's possible that the nation's 95,000 miles of coastline might provide other entry points to enterprising and ambitious aliens.

So we can construct a multi-billion-dollar Maginot Line on the border with Mexico. And our politicians can chest bump one another in celebration of their border toughness. But if we don't address illegal immigration at the point of employment, whatever we do at the border will be a colossal waste of money. We think we can build an impermeable wall. But we are everywhere surrounded by Belgium.

(Francis Wilkinson is a member of the Bloomberg View editorial board. Follow him on Twitter.)