Due to the frontierization of nation-states, maritime historians have tended to ignore the northern Bay of Bengal. Yet, this marginal region, now dispersed over the four nation-states of India, China, Myanmar and Bangladesh, was not marginal in the past. Until recently, however, historians have concentrated largely on the 'big four': the Gujarat, Malabar, Coromandel and western Bengal coasts. Extreme eastern South Asia -- Bengal and the lands to its north-east fanning into Burma and China, or modern India's north-east and beyond -- is the focus of Pelagic Passageways. This regional unit, including diverse topographic features: plains, forests, estuaries, deltas, rivers, mountains, lakes, plateaus and remote passes, oscillates between unity and fragmentation, between centrality and marginality in the larger space of the Bay of Bengal. To attempt a history of this space is indeed challenging. There is not one, but two deltas here: the western delta, corresponding to present West Bengal in India and centred now on Kolkata, and the south-eastern delta, in present Bangladesh, centred on Dhaka, and running into Arakan. Not merely in terms of location, but on a historical axis too, the two deltas are vastly different as they have followed disparate trajectories, dictated in part by their geographies. Pelagic Passageways, therefore, questions the conventional fault line, located on the south-eastern Bengal delta, between the historiography of South and South-East Asia. Concentrating on commodity and currency flows, travel, trade, routes and interactive networks Pelagic Passageways visualizes the cultural space of the northern Bay of Bengal as embracing upland landlocked areas -- Ava, Yunnan, the Tripuri, Dimasa and Ahom states -- not usually seen as part of maritime history. This collection of essays suggests that they too were a part of the social and commercial networks of the Indian Ocean. While these countries literally fell off the map, this volume proposes that we see these areas instead as crossroads, mediating flows between the land-dwelling and aquatic worlds.