Source: TW
The daftar of the Mogol tyrants of India has its roots in koko debter (the blue register) which was initiated by Shigi Qutuku the foster son of Chingiz Khan at his behest. The koko debter was first initiated in 1206 CE & included a census of the subjects of the Mongol Khaghanate. At 1st, the census only included the steppe peoples. In the time of Mongke Khan it was extended to the chIna, the rUs, and Mohd subjects. In 1235 CE S.Qutuku& Yelü Chucai carried out a massive census of the chIna-s for the debter. One of biggest pre-modern census efforts was that of Mongke in 1252 CE spanning much of their empire. It covered chIna, rUs, Iran and the Caucasus in addition to the core steppe lands.
The rUs, “chronicle of Novgorod” records it with anger: “And the accursed ones/infidels started riding streets writing down the numbers of the Christian households.” Actually, Mongke was quite considerate in his policy for drafting. He passed an edict checking that the draftees be drawn only from large families so that contributing a male will not result in a loss of a worker for their guild, realizing the need to balance economic output with respect to military manpower. Practicing Chinese & bauddha scholars were also given exemptions from draft.
The Mongols stored the debter as paper records in Mongolian, Uighur & probably also Chinese at Qara Qorum & unfortunately except for few paraphrases in Chinese Yuan Shih the data has been lost. It would have been a remarkable data source from the mid-1200s had it survived!
Interestingly, the Mongol census records of households involved in the military were kept separate & secret. They could be accessed only by the inner circle of the Chingizids. This suggests that there was a certain concern for security reasons of these numbers being leaked out.