Among them is what, if anything, Mr. Assange knew about Guccifer 2.0, a hacker whom U.S. officials have identified as a front for Russian operatives.

Mr. Assange, bearded and bedraggled, was dragged from the Ecuadorean Embassy in London, where he had been sheltered since 2012. He was charged in the U.S. with conspiring to hack into a Pentagon computer network, as part of the process that brought WikiLeaks a trove of classified U.S. material in 2010. The narrow indictment was a relief to some of those who feared a case against Mr. Assange could undermine press freedoms. We explained those concerns.

Closer look: From his beginnings as a teenage hacker in Australia, Mr. Assange has been a deeply divisive figure. Two of our reporters traced his history.

What’s next: Mr. Assange indicated that he would fight extradition, and legal experts said that the process could take years. He is likely to argue that the case is politically motivated.