Mr. Erdogan’s own statements have also raised questions about the sequence of events. In an account posted on the president’s website, Mr. Erdogan said he was first warned of unusual military activity at 4:30 p.m. by his brother-in-law. He tried to contact Mr. Fidan and Mr. Akar around 5 p.m., he said but was unable to reach either of them.

The confusion about what happened in the hours leading up to the coup last July has led to speculation among the Turkish opposition that the government may have allowed the coup to unfold, or even encouraged it, in order to justify the subsequent crackdown. The leader of Turkey’s largest opposition party, Kemal Kilicdaroglu, has described what happened as a “controlled coup.”

Why was the coup so poorly executed?

At the onset of the coup, rebel soldiers began blocking roads and bridges around 10:30 p.m. on a Friday night — a time when most Turks were still up and about, and therefore an odd moment to commence an operation that relied on surprise. Some observers have suggested that the coup was meant to begin much later in the night, but was rushed forward after coup leaders realized that their plans had been uncovered.

Other decisions are harder to explain. The coup plotters raided the state broadcaster, T.R.T., early in the evening but did nothing about most of the country’s private television channels. Those channels put government officials on the air throughout the night, letting the government control the narrative. And while the plotters tried to seize Mr. Erdogan, few attempts seem to have been made to round up other important government figures.

The attempt to kidnap Mr. Erdogan was bungled. The soldiers sent to seize him did not reach his vacation hotel until several hours after the coup began. In a recent court hearing, one of them, Brig. Gen. Gokhan Sonmezates, said they had been ordered to wait, a decision he found strange. “Who misled us,” General Sonmezates asked, “and made us wait for four hours?”

What did foreign powers know?

In Turkey, foreign governments were seen as responding slowly and tentatively to the unfolding events, prompting Mr. Erdogan’s supporters to suggest that the coup had the tacit support, or at least happened with the foreknowledge, of Turkey’s allies, including the United States. No evidence of this has surfaced, but the fact that Mr. Gulen lives on American soil has fed speculation that foreign officials must have been tipped off.

Statements by Michael T. Flynn, the retired American general who later served briefly as President Trump’s first national security adviser, seemed to strengthen this impression. Speaking as the coup unfolded, Mr. Flynn suggested that he had been briefed on the operation by a friend in the Turkish officer corps, and expressed his support. (He later reversed his position and blamed Mr. Gulen for the coup, casting some doubt on how much Mr. Flynn had actually known at the time.)