The US government has completed its case against Bradley Manning, the source of the massive WikiLeaks trove of state secrets, accusing the 25-year-old soldier of being a traitor who used his training and skills to deliberately and systematically harm the US and provide assistance to al-Qaida.

Major Ashden Fein, the lead prosecutor, unleashed a wave of rhetoric against the army private at the conclusion of his closing arguments in Fort Meade, Maryland, where the trial is in its eighth week. At the culmination of almost four hours in front of the judge, Fein sought to press home the most serious and contentious charge against Manning – that he knowingly "aided the enemy" by transmitting state secrets to WikiLeaks.

"He was not a humanist; he was a hacker who described his fellow soldiers as 'dykes' or 'global idiots'. He was not a troubled young soul; he was a determined soldier with the ability, knowledge and desire to harm the US. He was not a whistleblower; he was a traitor."

Fein cast Manning and Julian Assange, the founder of WikiLeaks, as "information anarchists". While the soldier's defence team has sought to portray Manning as naive and well-intentioned, the prosecutor countered that "he acted in a calculated manner for his own purposes – the only naivety he showed was that he actually thought he would get away with what he did and not get caught."

Manning faces 21 counts relating to his transmission in 2009-10 of more than 700,000 official documents to WikiLeaks, including war logs from Iraq and Afghanistan, diplomatic cables, detainee files from Guantanamo and a video of an Apache helicopter attack that killed civilians in Baghdad. He faces a maximum sentence of life in military jail plus 154 years, on top of up to 20 years in custody for a lesser version of the charges to which he has already pleaded guilty.

The prosecution team reserved its most forceful denunciation of Manning for the "aiding the enemy" charge – the most severe charge that has been widely criticised for potentially sending a chill across freedom of the press in the US. To make the charge stick, the US government has to prove that the soldier had an evil intent to disclose information knowing that it would be accessed by enemy groups such as al-Qaida and al-Qaida in the Arabian peninsula (Aqap).

Fein said that Osama bin Laden had personally asked for and received elements of the WikiLeaks documents including Afghan war logs and US diplomatic cables. Manning was fully aware in his training "who the enemy was and what type of information they sought, he knew the enemy used the internet and that WikiLeaks was helpful to our enemies."

He continued that Manning "had a general evil intent. The US has proved beyond a reasonable doubt that his voluntary actions to disclose more than 700,000 documents would lead to them being in the hands of the enemy."

The prosecutor drew on the testimony of more than 80 state witnesses to attempt to show that the Army private was fully aware of the consequences of his actions. Fein screened training presentations that Manning had been shown during his induction as an intelligence analyst that explained various classification levels and his own personal responsibility for guarding the secrets.

"He was trained that the enemy used the internet, and anything that the enemy used against the United States should be protected. He had actual knowledge that the enemies of the US used the internet and WikiLeaks to gather information to be used against this country," Fein said.

In earlier testimony from defence witnesses, Manning's legal team has attempted to define WikiLeaks as a journalistic enterprise equivalent to established news outlets such as the New York Times or the Washington Post. The distinction between such outlets and other activist groups is important, as it would help the defence rebut the charge that Manning "aided the enemy".

But the chief prosecutor in the case attempted to paint a very different picture of WikiLeaks and its founder, Assange. Fein quoted from web chats between Manning and Assange that remain classified, alleging that within two weeks of having gained access to secret databases in Iraq the soldier had begun actively searching for information that WikiLeaks wanted to disclose.

"PFC Manning saw WikiLeaks as anything but a traditional journalistic organisation … He identified WikiLeaks as the first intelligence agency for the general public."

In one part of the web chats, Manning wrote to Assange: "Government organisations can't control information, the harder they try the more violently the information wants to get out."

Fein continued that setting aside the argument that "sending classified information to an established journalistic organisation such as the New York Times would be a crime, that is not what happened in this case. He disclosed information to WikiLeaks knowing that WikiLeaks would release information in the form that it received it. WikiLeaks was merely the platform to make sure all the information was available to the world including the enemies of the United States."

The prosecutor tried to discredit the defence testimony from Yochai Benkler, a Harvard law professor and expert in social media, who previously told the court that WikiLeaks was indeed a journalistic organisation. Fein decried Benkler's evidence as having been "faulty" and based on "bias and misinformation".

Once the prosecution has completed its closing arguments, Manning's leading defence lawyer, David Coombs, will have his chance to persuade the judge. The US government may then have an opportunity to rebut defence closing arguments, before Lind retires to consider her verdict which could come in a matter of days.