Because this king was the one who kept stopping Arab armies — and Sulaiman, writing from the Arab side, described a military enemy in religious words. The opposition was political and territorial; the label is his interpretation of it.
The evidence in the chapter
- The Gurjara-Pratīhāras “gained fame for pushing back Arab invasions into northwest India”.
- When the Arabs pushed into Rājputāna and Mālwā, the Gwalior inscription records that Nāgabhaṭa I “crushed the large army of the powerful Mlechchha king.”
- Sulaiman’s own words explain the resentment: this king had the finest cavalry in India, numerous forces, riches, camels and horses. He was simply the hardest opponent the Arabs met on that frontier.
Why he used religious language for a military fact. In the 9th century, Arab expansion was carried out in the name of faith — the Chachnāma has bin Qasim quoting the Quran to King Dāhar. To a writer inside that world, a ruler who blocked Arab armies was naturally described as an enemy of the faith rather than as an enemy of the caliphate’s ambitions. It is the same fact seen through a religious lens.
And notice what Sulaiman does not say. He does not report that this king persecuted Muslims, closed mosques or forced conversions. Compare Al-Masūdī on the Rāṣhṭrakūṭa ruler in whose kingdom “Islam is honoured and protected”: the Rāṣhṭrakūṭas were not fighting the Arabs on a frontier, and Muslim traders lived well on their coast. The difference between the two reports is not a difference of religious policy — it is the difference between a frontier at war and a coast at peace.