A national guardsman accused of leaking highly classified military documents is due to appear in court later today.

Jack Teixeira is set to be charged with removing or transmitting classified national defence information, which is a crime under the National Espionage Act.

The 21-year-old’s arrest raises fresh questions about America’s ability to safeguard its most sensitive secrets, and the Pentagon has vowed to tighten security measures.

Ukraine war latest: Suspected Pentagon leaker is named; jailed Putin critic ‘has mystery illness’

It described the leak as a “very serious risk to national security” – but officials are coming under pressure to explain why such a young, low-ranking service member had access to these files.

The material was shared on a chat group called Thug Shaker Central, which was based on Discord.

It had about 25 members who also discussed their favourite types of guns and shared memes – some of them racist.

While Teixeira’s motive is unclear, other members of that chat group have claimed he was driven by bravado more than ideology.

Teixeira had served as an IT specialist responsible for protecting military communication networks – and according to one defence official, this meant he would have had a higher level of security clearance.

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Inside the Pentagon leaks

The classified documents included briefing slides mapping out Ukrainian vulnerabilities and military positions, as well as information on the circumstances where Vladimir Putin might use nuclear weapons.

Information about allies including Israel, South Korea and Turkey was also included, in what is believed to be the most serious security breach since 700,000 documents, videos and diplomatic cables appeared on WikiLeaks back in 2010.

Several countries had questioned whether some of the leaked documents were authentic, with British officials claiming there was a “serious level of inaccuracy” in the information. However, US officials do believe most of the materials are genuine.

Mike Turner, the Republican chairman of the House Intelligence Committee, has pledged to “examine why this happened, why it went unnoticed for weeks, and how to prevent future leaks”.

Read more:
What do the highly classified documents say?

How did someone so young have access to such sensitive files?

It appears that the American authorities have been on the backfoot at every turn with this case.

They now claim to have their leaker. He will go through the judicial process.

They will be relieved, at least, that he appears not to be a foreign agent.

But they have many questions to answer: how did a 21-year old Air National Guardsman have access to these documents?

Was he entitled to the access? Are there more classified documents out there? Why did it take so long, with media help, to find him?

Read Mark’s full analysis here.

The Pentagon – which called the leak “a deliberate, criminal act” – says the military is also reviewing distribution lists and ensuring people who receive classified information have a need to know.

While the documents were posted online last month – perhaps earlier – they only broke into wider circulation last week.

The New York Times had first reported Teixeira’s identity, and federal officials later confirmed he was a subject of interest in the investigation.

News crews in helicopters later filmed his arrest in Massachusetts, and the young guardsman was wearing a T-shirt and shorts as heavily armed tactical agents took him into custody.

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Biden ‘not concerned’ about leaks

In a statement, the FBI said: “Since late last week the FBI has aggressively pursued investigative leads – and Thursday’s arrest exemplifies our continued commitment to identifying, pursuing and holding accountable those who betray our country’s trust and put our national security at risk.”

Teixeira may also face charges in military court – and one former prosecutor has suggested he could face up to 10 years’ imprisonment if convicted.

Brandon Van Grack explained: “I think this is someone who is facing on the higher end of exposure for years in prison … because the leaks were so damaging.”

President Joe Biden, speaking on his three-day tour of Ireland, told reporters: “I’m concerned that it happened, but there is nothing contemporaneous that I’m aware of.”