WASHINGTON — The WikiLeaks founder Julian Assange was arrested on Thursday in London to face a charge in the United States of conspiring to hack into a Pentagon computer network in 2010, bringing to an abrupt end a seven-year saga in which he had holed up in Ecuador’s embassy in Britain to avoid capture.

The Ecuadorean government suspended the citizenship it had granted Mr. Assange and evicted him on Thursday, clearing the way for his arrest. His hosts had displayed growing impatience, listing grievances including recent WikiLeaks releases they said interfered with other states’ internal affairs and personal discourtesies, like the failure of Mr. Assange to clean the bathroom and look after his cat.

A bedraggled and shackled Mr. Assange, 47, was dragged out of the embassy. At a court hearing, a judge swiftly found him guilty of jumping bail, and he was detained partly in connection with an American extradition warrant. Mr. Assange indicated that he would fight extradition, and legal experts said that process could take years. He is likely to argue that the case is politically motivated rather than driven by legitimate legal concerns.

Mr. Assange’s arrest brought to a head long-simmering tensions that have raised profound First Amendment press freedom issues. Since Mr. Assange began publishing archives of secret American military and diplomatic documents in 2010 — provided by the former Army intelligence analyst Chelsea Manning — senior officials in two administrations had weighed whether to try to put him out of business by charging him with a crime. Ms. Manning was convicted at a court-martial trial in 2013 of leaking the documents.