Despite his claim on Tuesday that he is taking an almost unprecedented step, Donald Trump is not the first commander in chief to deploy troops to the US-Mexico border.

Barack Obama sent 1,200 members of the National Guard to the frontier in 2010, following on from George W Bush’s decision four years earlier to boost the military presence there.

“The United States is not going to militarize the southern border. Mexico is our neighbour, and our friend,” Bush insisted in 2006 in a speech on immigration reform that nonetheless announced a large increase in the number of border patrol agents and the deployment of up to 6,000 National Guard members in a two-year operation dubbed Jump Start.

They built infrastructure such as roads and fences and conducted surveillance on the ground and in the air, but left it to the border patrol to make arrests – because of the troops’ lack of expertise in border enforcement and limits on the tasks that active duty military forces can perform domestically.

Obama’s move came at a moment of heightened political tension over border security, with prominent Republicans including John McCain, the Arizona senator, worried about drug cartel violence and demanding enhanced measures, as tighter security in California increasingly led migrants to find entry points to the east.

Several hundred National Guard troops were already on the border to combat the cartels.

Like Bush, the Democratic president hoped, in vain, that a greater military commitment would help bring Republicans to the table for negotiations that would lead to comprehensive immigration reform, including a path to citizenship for many of the estimated 11 million undocumented immigrants in the US.

The National Border Patrol Council, a union, welcomed the help of the National Guard in conducting aerial surveillance. But a 2012 report by the Government Accountability Office questioned the usefulness of the Bush and Obama operations, which together cost about $1.35bn.

The report found that there were some benefits from the cooperation, such as a deterrent effect on criminals, and building relationships between various law enforcement branches, but the military’s border assistance was “ad hoc” and lacking a precise role in a clearly-defined strategy.

Also – not that this is likely to disturb the White House in the current political climate – there were worries that the perception of a militarised border could damage relations with Mexico.

Many migrant advocate groups argue that given the scale of the armed law enforcement presence, the extensive surveillance infrastructure, fencing and numerous checkpoints, the border is, in effect, already militarised.

Texas has spent hundreds of millions of dollars to supplement federal border enforcement programmes. In 2014, amid a surge of Central American families and unaccompanied children crossing the border, Rick Perry – then the Texas governor, now federal energy secretary – ordered state law enforcement officers and the National Guard to the frontier.

The state purchased six high-powered gunboats and Perry toured the border with Sean Hannity, the Fox News host.

In 2015, Perry’s successor as governor, Greg Abbott, signed into a law a bill directing the state to lay out $800m on border security over two years.

State lawmakers committed last year to carry on spending, despite Trump’s election, the decrease in unauthorised border crossings and the reality that many migrants surrender to US officials as soon as possible in order to seek asylum.

The National Guard troops did not make arrests, with their presence seemingly designed mainly as a deterrent.

An analysis by KXAN local news in 2016 found that most border arrests by state troopers were for drunk-driving and minor drug violations, not the smuggling of people or drugs.

Overall, despite Trump’s rhetoric, there is no evidence of an immediate crisis that might call for a drastic response. Border crossings have declined significantly since the mid-2000s, and border patrol statistics show that the number of arrests on the south-west border – an indicator of the rate of illegal crossings – has plunged in this fiscal year compared with last. Apprehensions of unaccompanied children are down 36%, and those of families have fallen by 46%.