Iltazar's younger brother Mohammed Rakhim was made Khan, and was soon hot on the heels of the Yomut Turkomans, driving them out of the capital and obtaining considerably more booty than had been taken by the Yomuts in the first place. No sooner had the Yomuts been dealt with than the Karakalpaks began to revolt, followed by a rival bid for the throne by a relative in Kungrad.
Mohammed Rakhim Khan laid siege to Kungrad amidst jeers from the local citizens, who shouted down from the walls that within the city they had enough resources to survive three months of the year on sour milk, three months on melons, three months on pumpkins and three months on fish. This did not deter the obstinate Khan who laid seige to the city for 17 long years.
Whilst laying siege to Kungrad, the Khan also decided to avenge his father's death and attacked Bukhara. Ravaging the city and its surrounding provinces, he returned laden with bounty and opened Khiva's first mint, producing gold and silver coins.
The Khan then set about assuring his legitimacy and married into the Said clan (descendents of the Prophet Mohammed), affixing Said to his name. He set up an 11-member parliament and introduced Sharia law to the Khanate. He also promoted scholars and scientific work and commissioned a mausoleum for Pakhlavan Mahmoud. Tall and strong, with a striking yellow beard, Mohammed Rakhim struck an imposing image. Speaking Turki, Persian and Arabic, he was also a skilled doctor and was known as Mohammed Rakhim the Learned.
However, according to Captain Muraviev, the Russian diplomat-cum-spy, the Khan may have been learned, but he certainly was not civilised, describing him as a cruel barbarian who had killed most of his relatives and those who were potential threats to the throne as well as anyone standing in his way.

'He was tall and powerfully built. His features are regular, the eyes small but fiery and piercing, and his beard short and foxy. It is strange that his eyes should be the only part of his face at all characteristic of his nation, and that otherwise he much more resembles a Russian than a Khivan.'

He describes him as having:

'A clear intellect, quick perception, ambition, monstrous cruelty, love of power, enterprise, intrepidity, extraordinary determination, covetousness, and suspicion.
His mode of living is quite nomadic, for he occupies a felt tent all the year round, keeping his houses for his wives only. (He had only seven).'

Muraviev, suspected of being a spy, only just escaped with his life. Attempting to be diplomatic, he presented the Khan with a set of nine fine brandy glasses (ten being considered an unlucky number).

'The Khan had been immensely delighted, and had examined each glass separately, repeating, "What a pity! What a pity that they did not send me these in the days when I drank brandy!" It turned out that he had formerly been much addicted to this beverage, but had now entirely renounced the use of spirituous liquors and tobacco. He had even prohibited smoking among his subjects, and proclaimed that disobedience in this matter would entail the delinquent's mouth being cut up to the ears.... Among the Khan's gifts there was also a glass 'Kaliyan' (hookah stand), which puzzled him very much. The Yuz Bashi did not venture to tell him the truth, so said it was a vessel for holding vinegar, which he had a great fondness for.'

Nicholai Muraviev 'Journey to Khiva through the Turkoman Country'
English Edition, 1871

The Kahn's sensitive conscience did not, it would appear, extend to compassion towards the multitudes of slaves, many of them also Muslims, who languished in Khiva. Muraviev had witnessed their plight and vowed to do something about it. He was eventually allowed to return to Russia safely, after the Khan decided it prudent not to antagonise Russia by assassinating their trade emissary and spy. Gaining an audience with the Tsar, Muraviev begged him to help the enslaved Russians in some way, thus providing Russia with the perfect pretext for an invasion.