The latest data from Homeland Security show that there has been a sharp increase in the number of illegal aliens crossing the southwest border of the U.S. 

Almost 40,000 illegals were caught trying to cross the border last month, up 12% since October and more than twice the number from last March.

Washington Times:

Homeland Security said overall things are still an improvement over the worst years of President Obama.

"Under President Trump, illegal immigration has declined dramatically over the last year," said spokesman Tyler Q. Houlton.

But he said more needs to be done, and said action needs to come from Capitol Hill.

"The administration is working tirelessly to secure the border, enhance interior enforcement and establish a merit-based immigration system. But we need Congress to act immediately to close immigration loopholes, fund the border wall, terminate outdated visa programs and provide the necessary tools for DHS officials to carry out their mission," Mr. Houlton said.

The 39,006 people caught in November included 29,086 caught by the Border Patrol, and 9,920 who tried to come through official ports of entry without permission. The total is still less than 2015 or 2016, but is more than 2012, 2013 or 2014, signaling a return to Obama-era levels of illegal immigration on the border.

Just last week the Trump administration crowed over its gains, pointing to a nearly 30 percent decline in people being caught at the border compared to the previous year. But they did say they were "very concerned" by the latest trends, which have been born out in Friday's numbers.

CBP officials said cartels have figured out how to "exploit legal and policy loopholes" in the U.S. to get illegal immigrants into the country and give them a chance to blend into the shadows.

There are several possible explanations for the surge.  The threat of increased enforcement could be driving some of the increase.  The prospect of a wall going up on the border may also be a spur to illegal immigration.

But a likely culprit for the increase is that the border patrol is losing agents faster than it can replace them.  This despite the president's goal of hiring 5,000 more agents.

More than 900 agents leave each year on average but the Border Patrol only hires an average of 523 a year, the Government Accountability Office said in a broad survey of staffing and deployment challenges at the key border law enforcement agency.

The law requires the agency to have a minimum of 21,370 agents on board, but it had just 19,500 agents as of May.

That's an even bigger problem when stacked up against President Trump's call for hiring 5,000 more agents, to reach a workforce of 26,370.

Fewer agents patrolling the border means that the mules who are leading groups of illegals into the U.S. can find unguarded or lightly guarded routes that gives them a bigger chance of success.

The surge in illegal crossings makes a stronger political case for the president's campaign promise to build a wall.  Congress has yet to authorize any money to construct the barrier, with Democrats promising to shut down the government rather than appropriate any money for the wall.