American drones were decimating the upper ranks of al-Qaida, his men were killing suspected spies, and Osama bin Laden wondered: Could an Iranian dentist have planted a tracking device in his wife's tooth?

"The size of the chip is about the length of a grain of wheat and the width of a fine piece of vermicelli," he wrote, using the nom de guerre Abu Abdallah.

After conducting the raid on Laden’s compound in Pakistan's Abbottabad in May 2011, the letter was among the several documents and other materials seized by the Navy seals, and was declassified, yesterday.

A document appeared to be a will written by Laden, revealed that, the deadly terrorist had about $29 million in Sudan. He asked to spend the same on Jihad, if he was killed.

The documents supported in proving a glimpse of Laden's thinking, during his final years, and the struggle to keep al-Qaida's main branch and its offshoots in line and focused as American drone strikes demoralized its foot soldiers.

There are many other documents which are yet to be declassified. But the documents released so far states that, the fear of being tracked is a theme that resurfaces again and again. In one letter, Laden warns that a suitcase used to deliver a ransom could contain a tracking device.

Another author unidentified letter revealed a group of men coming from Qatar with GPS devices, with Afghanistan map. They were accompanied by a Qatari diplomat, who left three days later, saying he had diabetes and needed medication. The departure appears to have made the Qaida members suspicious, and one militant, identified by the pseudonym Abu Umamah "smashed it with a hammer," the document reads.

With the aim of imposing bureaucratic uniformity across his terrorist network, the struggle Laden took was dealt in the documents.

Naming the course as “Course of Islamic Study for Soldiers and Members”, it includes a list of subjects and skills to be taught for the new fighters.

By Phani Ch