Since 2019, Julian Assange, the founder of WikiLeaks, has been held in a high security prison in southeast London while his lawyers fight a U.S. extradition order. Now, that particular battle may be nearing its end.

On Tuesday and Wednesday, Mr. Assange’s case returns to a British court for a two-day hearing that will determine whether he has exhausted his right to appeal within the U.K. and whether he could be one step closer to being sent to the United States.

In America, Assange, 52, faces charges under the Espionage Act of 1917 that could amount to a sentence of up to 175 years in prison, his lawyers say, although lawyers for the United States government had previously said that he was more likely to be sentenced to between four and six years. Here’s what to know about the long-running legal battle over his extradition and what could happen next.

Assange has been in a British prison for nearly five years. Here’s why.

The U.S. charges against Mr. Assange date to events in 2010, when WikiLeaks published tens of thousands of secret military and diplomatic documents leaked by Chelsea Manning, an Army intelligence analyst.

The files exposed hidden diplomatic dealings and included revelations about civilian deaths in the wars in Iraq and Afghanistan.

In May 2019, during the Trump presidency, the U.S. Justice Department accused Mr. Assange of violating the Espionage Act by soliciting and publishing secret government information, charges that raise profound First Amendment issues. (The Obama administration had considered charging Mr. Assange but decided against it because of the threat to press freedom.)