Flanked by two masked men holding assault rifles, the self-styled commander-in-chief spoke calmly in a video now widely circulated online with these subtitles: "We are on (a) defensive war against the Burmese (sic) brutal (sic) military regime in Maungdaw, Buthidaung and Rathedaung" (townships).
The man is Ata Ullah, known at various times as Ameer Abu Amar, Abu Amar Jununi or Hafiz Tohar.
He is the Pakistan-born leader of the Arakan Rohingya Salvation Army (Arsa), which launched attacks on Myanmar security forces with surprising sophistication on Aug 25.
In the video released that day, he declared: "This land is called Arakan and belonged to Rohingya. My call for the Rohingya nation is also the call from all Rohingyas."
According to a report by International Crisis Group, Ata's father was a Muslim from Rakhine state who went to Karachi. After the birth of Ata, the family moved to Saudi Arabia, allowing the boy to receive a religious education in Mecca.
Ata, who is 27 years old according to Agence France-Presse, has a fluent command of both Arabic and the Bengali dialect used by the Rohingya Muslim minority in Rakine. He is thought to have received training in modern guerilla warfare.
His group, which drew initial attention last October with a raid on three police posts in Rakhine, was initially called Harakah al-Yaqin, or "faith movement" in Arabic.
It changed its name to Arsa in March.
Although Ata has denied links to international Islamist movements, Arsa has sought and obtained fatwas, or religious rulings from clerics, in countries like Pakistan, India, Saudi Arabia and Bangladesh, to legitimise its campaign against the Myanmar security forces.
Arsa has also been accused of murdering government collaborators - including Muslims - to intimidate villagers against telling on them, though a Twitter account purportedly belonging to Arsa has denied this.
In a video released on Aug 29, Ata condemned alleged atrocities committed by Myanmar's security forces against Rohingya civilians and warned other ethnic groups not to be tricked into confronting the Rohingya.
"Our war is only with the (Myanmar) military," he said.
"Therefore our war is not with the Rakhine or any other ethnic group."