An affidavit detailing the alleged crimes of Julian Assange was unsealed Monday, revealing more about what investigators knew regarding the WikiLeaks founder’s communications with former Army intelligence analyst Chelsea Manning.

Assange, 47, was arrested Thursday at the Ecuadorian Embassy in London in connection to a charge in the U.S. of conspiring to hack into a Pentagon computer network in 2010.

A possible arrest and extradition to the U.S. had been expected in recent months after prosecutors mistakenly revealed in November that the Justice Department had secretly filed criminal charges against Assange. Following a U.K. Supreme Court ruling that he should be extradited to Sweden for questioning over sexual assault charges, Assange sought and was granted political asylum in the Ecuadorian Embassy in London in 2012. He remained there until metropolitan London police arrested him last week.

[WATCH: WikiLeaks founder Julian Assange dragged out of Ecuadorian Embassy in London by police]

The disclosure of a sealed indictment against Assange, which came during special counsel Robert Mueller’s investigation, led to speculation that it was related to WikiLeaks’ role in disseminating emails stolen from Democratic officials during the 2016 election. The U.S. intelligence community believes Russian hackers were behind the theft.

But the indictment, unsealed last week, revealed Assange had not been charged in connection with Russian interference in the election nor had he been charged for publishing government secrets contained in the documents leaked by Manning almost a decade ago. Instead, prosecutors charged him with conspiracy to commit computer intrusion by agreeing to help Manning crack a password that would have given her access to a classified military network.

The single-count conspiracy indictment against Assange carries a maximum penalty of five years in prison, but national security experts speculate that there could be a slew of additional charges — including espionage — leveled at Assange if and when he is extradited to the United States.

FBI special agent Megan Brown wrote in the 26-page affidavit filed in December 2017 Assange and Manning allegedly tried to gain access to the Pentagon network, but “it remains unknown whether Manning and Assange were successful in cracking the password.”

The indictment against Assange acknowledged an alleged agreement between Manning and Assange for the latter to help break a system to which Manning did not have access, though it did not indicate whether investigators knew if the system was breached.

Investigators said they were able to uncover the alleged crime by obtaining hundreds of chats from March 2010 between Assange and Manning on Jabber, an instant messaging platform.

Brown also wrote in her affidavit that Manning and WikiLeaks “had reason to believe that public disclosure of the Afghanistan War Reports and Iraq War Reports would cause injury to the United States.” Brown said the war reports purloined by Manning and disseminated by Wikileaks “contained information the disclosure of which potentially endangered U.S. troops and Afghan civilians, and aided enemies of the United States.” The reports contained potentially harmful identifying information about local allies on the ground who were assisting U.S. and coalition forces.

The affidavit also alleged the Taliban exploited the WikiLeaks disclosures to put U.S. allies in danger, citing a New York Times article headlined, “Taliban Study WikiLeaks to Hunt Informants.” It also said the raid on Osama bin Laden’s compound in Abbottabad, Pakistan, showed that the terrorist was actively seeking information contained in the WikiLeaks disclosures and that al Qaeda was providing him with information from the leaked Afghanistan war reports. The Afghanistan war reports also contained specifics on improvised explosive device techniques and countermeasures espoused by the U.S. that “the enemy could use these reports to plan future lED attacks,” the affidavit said.

The criminal complaint that was unsealed last week alleged Assange encouraged Manning to hand vast amounts of classified information over to WikiLeaks to disseminate. “These databases contained approximately 90,000 Afghanistan war-related significant activity reports, 400,000 Iraq war-related significant activity reports, 800 Guantanamo Bay detainee assessment briefs, and 250,000 U.S. Department of State cables,” DOJ said.

Assange's attorneys say he plans to fight the extradition proceedings in London, which could drag on for months or longer. It's likely that Assange could eventually appeal his case to a higher British court and perhaps even to the European Court of Human Rights.

Manning, formerly known as Bradley, was convicted at a court martial trial in 2013 of leaking a trove of documents to WikiLeaks. Sentenced to 35 years in prison, Manning's sentence was commuted by former President Barack Obama just days before the end of his presidency in January 2017. Manning was recently imprisoned again after refusing to provide grand jury testimony in relation to the WikiLeaks case.