TAIPEI, Taiwan — Taiwan on Wednesday named a military man as its new defense minister, less than 24 hours after his civilian predecessor resigned just six days into his tenure.

The appointment of career air force officer Yen Ming to the position raises questions about a possible power struggle over the defense minister's job, which has taken on added significance following the death of a 24-year-old conscript in a military brig and growing Defense Ministry difficulties in transitioning to an all-volunteer force.

Yen, 64, replaces Andrew Yang, a respected academic, who announced his resignation late Tuesday after taking responsibility for an article that a ghost writer prepared under his name in a 2007 book on China's People's Liberation Army that contained material lifted from another source.

President Ma Ying-jeou accepted Yang's resignation immediately. The speed of his action prompted suggestions that senior military officials had made Ma aware of their unhappiness over Yang's appointment, ostensibly because of his reformist credentials and presumed inclination to threaten longstanding military prerogatives.

Speaking to reporters early Wednesday, Defense Ministry spokesman Lo Hsiao-ho denied any suggestion of a power struggle within the ministry.

But lawmaker Lo Shu-lei from Ma's own Nationalist Party charged that ministry officials had leaked the material on Yang as a way of forcing him to resign.

"The military is definitely behind the resignation of Yang," she said. "This is a counterattack from someone who failed to become minister."

Allegations about Yang's purported transgression were first bruited on the day of his appointment, but Lo insisted they had been well known to ministry officials for years, including the four-year period when Yang served as deputy defense minister.

"Why did he have to become defense minister before he was attacked and not when he was deputy defense minister?" she asked. "After all, the allegations are not new."

Yang, 58, took office last Thursday after his predecessor resigned amid a furor over the death in early July of an army conscript forced to perform grueling exercises in searing heat while being held in a military brig over a cellphone violation.

The death of university graduate Hung Chung-chiu just days before his discharge infuriated many Taiwanese, who saw it as another in a long line of military abuses. An estimated 200,000 protesters took to the streets of Taipei on Saturday demanding far-reaching military reforms, including civilian control over important elements of the military justice system.

Eighteen officers and noncommissioned officers, including a general, have been indicted in connection with the Hung case.

The new defense minister's first operational challenge will be to implement the military's ambitious program to transition to an all-volunteer force by 2015, which even before Hung's death had been falling far short of its declared goals.

Now, after weeks of negative publicity over the death's grisly circumstances, the effort may have to be scaled down substantially.

Yang was the first civilian appointed by Ma to the prestigious defense post. A widely respected academic, he had been deputy defense minister since 2009.

His departure may yet come back to haunt the president politically, particularly with his approval ratings already hovering in the high teens to low 20s. Once praised for bravely lowering tensions with China — the two sides split amid civil war in 1949 — Ma has recently run into trouble, highlighted by his poor economic stewardship, his repeated administrative bungles and his perceived personal haughtiness.