Getting the Javanese to abandon the religion they had followed for more than 1, 000 years was not easy.
The Javanese number about 70 million, or more than a third of Indonesians.
It reveres the Islamic scholars, known by the Arabic term ulama or the Javanese term kiai, whose influence remains strong in east Java.
But many Indonesians believe that the influence of Javanese tradition on present-day politics goes much deeper than that.
Under the 32-year dictatorship of Suharto, which ended ten years ago this week, Indonesia, in keeping with the traditions of Javanese statecraft, used its clout discreetly.
Javanese leadership, the sultan explains, requires a king to control his own desires to serve the people.
"This is typical of a traditional Javanese king, the idea that he can do no wrong, " says Arbi Sanit, a political scientist at the University of Indonesia.
Migrants from Java, they were dispersed as part of the Indonesian government's decades-old transmigration program, designed to ease Javanese population pressures by encouraging relocation to the outer islands.
Ex-President Suharto, the country's deposed ruler, a Javanese, was, and presumably still is, deeply superstitious, being guided by his astrologer in important decisions.
The city's many ethnic communities - Javanese, Batak, Chinese, Melayu, Indian, Arab - have managed to stay fairly separate, each with their own way of life.
Many Javanese retain mystical religious beliefs that existed before the Islamic missionaries arrived.
Suharto created a New Order for the vast archipelago, and recreated himself as a new kind of Javanese king.
On a ridge near Sayan stands the unique Bambu Indah, a compound of 100-year-old royal Javanese houses.
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