It was unclear whether Mr. Abe was suffering again from the effects of that disease or had contracted another ailment.
During his second period in office, which began in late 2012, Mr. Abe survived a few influence-peddling scandals and rode out numerous elections. In 2015, he pushed through contentious security legislation that permitted Japanese troops to engage in overseas combat missions alongside allied forces, as part of “collective self-defense.”
His political power peaked in 2017, when his party won a landslide victory that gave it, along with its coalition partners, two-thirds of the seats in Parliament. That was the supermajority required to push through a constitutional revision, but Mr. Abe never brought that dream to fruition, with public opposition to such a change remaining high.
Mr. Abe, who was in office when Tokyo won its bid to host the 2020 Summer Olympics, will step down before he could preside over the Games, which were postponed to 2021 because of the pandemic.
By the time he signaled his intention to resign, Mr. Abe was a hugely unpopular leader whose disapproval ratings had risen to their highest level since he began his second term.
The public was dissatisfied with his administration’s handling of the coronavirus, particularly its effects on the economy, which erased what achievements he could claim under his economic platform, known as “Abenomics.”
Under that program, Mr. Abe had administered a three-pronged plan of monetary easing, fiscal stimulation and corporate reform. Most of its promises of corporate reform — including efforts to empower women, reduce the influence of nepotism and change entrenched work culture — remained unfulfilled.