What is the wall?

During the campaign, Trump was touting a 2,000 mile long, thirty feet high, concrete wall along the Mexican border, inspired by the Great Wall of China and some wall or other the Israelis have put up.

And probably, secretly, in his head, by the Berlin Wall.

Democrats generally and some Republicans, especially those from border regions, have opposed Trump's two thousand mile wall.

Trump has backed off to a wall about half that length, and recent modifications to his plan have concerned the materials of which the wall is to be made.

It is not entirely clear whether his proposal, now, is merely to replace and add a bit of length to the less than 700 miles of existing fencing, but in any case BBC, in a story dated 21 January 2019, says no design has been approved and no construction has taken place.

Considering that by far most illegals are people who arrive legally and then overstay their visas, while a good part of the people coming across from Mexico are legitimate asylum seekers, the wall seems a waste of good money on a wrong-headed cause.

But the Trump rabble like it, mostly out of white Nativism, it seems.

Before Mr Trump took office, there were 654 miles (just over 1,000km) of barrier along the southern border - made up of 354 miles of barriers to stop pedestrians and 300 miles of anti-vehicle fencing.

In the run-up to the 2016 presidential election, Mr Trump promised to build a wall along the border's entire 2,000-mile length.

He later clarified that it would only cover half of that - with nature, such as mountains and rivers, helping to take care of the rest.

. . . .

The 650 miles of fencing built under President George W Bush cost an estimated $7bn, and it could not be described as fulfilling Mr Trump's promises of a "tall, powerful, beautiful" barrier.

However, Mr Trump is now asking for $5.7bn in addition to the $1.7bn already allocated for new and replacement barriers.

The Department of Homeland Security (DHS) previously estimated a wall spanning half the border would cost up to $25bn, but it has now said it is still looking at options to determine the price tag.

US Customs and Border Protection (CPB) says that, on average, it costs approximately $6.5m per mile to construct a new border wall or replace existing legacy fence.

Oh, and this.

It was an eye-catching claim from the White House press secretary.

"Last year alone there were nearly 4,000 known or suspected terrorists that CBP picked up that came across our southern border," Sarah Sanders told Fox and Friends on Friday.

That is not true. Even her colleague, Kellyanne Conway, later called it "an unfortunate misstatement".

So where did that figure come from?

A White House briefing report on immigration says 3,755 known or suspected terrorists were prevented from entering the US in the fiscal year 2017.

But that includes terror suspects who have been stopped at any US border, and the vast majority are stopped at airports.

"The debate is over a land border wall. To include airport statistics is irrelevant and misleading," says Todd Bensman from the Center for Immigration Studies, a think tank which favours lower immigration.

Bensman, a former counter-terrorism intelligence manager who worked at the Texas border, analysed data from a "reliable intelligence community source" and concluded that more than 100 migrants on terror watchlists were apprehended at the southern border between 2012-17.

Data from NBC News seems to support his assertion. It learnt that in the first half of 2018 six immigrants on the terror watchlist were stopped at the southern border

No-one who has crossed the US southern border illegally from 1975 to the end of 2017 has been responsible for a terror attack on US soil, according to David Bier and Alex Nowrasteh of the Cato Institute.

Seven so-called "special interest aliens" were convicted of planning an attack on US soil, during that time, says the libertarian think tank's report.

But that category includes any visitor from a country deemed by the US intelligence community as a risk. In the past it has been a list of 50 countries.