Southeast Asian history has seen remarkable levels of mobility and durable connections with the rest of the Indian Ocean. The archaeological record points to prehistoric circulations of material culture within the region. Through the power of monsoon sailing, these small-scale circuits coalesced into larger networks by the 5th century bce. Commercial relations with Chinese, Indian, and West Asian traders brought great prosperity to a number of Southeast Asian ports, which were described as places of immense wealth. Professional shipping, facilitated by local watercraft and crews, reveals the indigenous agency behind such long-distance maritime contacts. By the second half of the first millennium ce, ships from the Indo-Malayan world could be found as far west as coastal East Africa. Arabic and Persian merchants started to play a larger role in the Indian Ocean trade by the 8th century, importing spices and aromatic tree resins from sea-oriented polities such as Srivijaya and later Majapahit. From the 15th century, many coastal settlements in Southeast Asia embraced Islam, partly motivated by commercial interests. The arrival of Portuguese, Dutch, and British ships increased the scale of Indian Ocean commerce, including in the domains of capitalist production systems, conquest, slavery, indentured labor, and eventually free trade. During the colonial period, the Indian Ocean was incorporated into a truly global economy. While cultural and intellectual links between Southeast Asia and the wider Indian Ocean have persisted in the 21st century, commercial networks have declined in importance.
Spatial distribution of the Southeast Asian smoke plume over the Indian Ocean and its radiative heating in the atmosphere during the major fire event of 2006