The history of Islam in Indonesia is complex and reflects the diversity of Indonesian cultures. There is evidence of Arab Muslim traders entering the Indonesian archipelago as early as the 8th century. Venetian explorer, Marco Polo is credited with the earliest known record of a Muslim community around 1297 AD, whom he referred to as a new community of Moorish traders in Perlak, Aceh. Over the 15th and 16th century, the spread of Islam accelerated via the missionary work of Maulana Malik Ibrahim (also known as Sunan Gresik, originally from Samarkand) in Sumatra and Java and Admiral Zheng He (also known as Cheng Ho, from China) in north Java, as well as campaigns led by sultans that targeted Hindu-Buddhist kingdoms and various communities, with each trying to carve out a region or island for control. Four diverse and contentious sultanates emerged in northern and southern Sumatra, west and central Java, and southern Kalimantan. The sultans declared Islam as a state religion and pursued war against each other as well as the Hindus and other non-Muslim infidels.