The Aksumite rulers facilitated trade by minting their own Aksumite currency, the state established its hegemony over the declining Kingdom of Kush and regularly entered the politics of the kingdoms on the Arabian Peninsula, eventually extending its rule over the region with the conquest of the Himyarite Kingdom. The Persian Prophet Mani regarded Axum as third of the four greatest powers of his time after Persia and Rome, with China being the fourth.