Kolkata (English: or , Bengali: [kolkata] (listen); also known as Calcutta , the official name until 2001) is the capital of the Indian state of West Bengal. Located on the eastern bank of the Hooghly River, the city is approximately 80 km (50 mi) west of the border with Bangladesh. It is the primary business, commercial, and financial hub of Eastern India and the main port of communication for North-East India. According to the 2011 Indian census, Kolkata is the seventh-most populous city in India, with a population of 45 lakh (4.5 million) residents within the city limits, and a population of over 1.41 crore (14.1 million) residents in the Kolkata Metropolitan Area. It is the third-most populous metropolitan area in India. In 2021, the Kolkata metropolitan area crossed 1.5 crore (15 million) registered voters. The Port of Kolkata is India's oldest operating port and its sole major riverine port. Kolkata is regarded as the cultural capital of India. Kolkata is the second largest Bengali-speaking city after Dhaka. It has the highest number of nobel laureates among all cities in India.In the late 17th century, the three villages that predated Calcutta were ruled by the Nawab of Bengal under Mughal suzerainty. After the Nawab granted the East India Company a trading licence in 1690, the area was developed by the Company into an increasingly fortified trading post known as Fort William. Nawab Siraj ud-Daulah occupied Calcutta in 1756, and the East India Company retook it the following year. In 1793 the East India Company was strong enough to abolish native rule, and assumed full sovereignty of the region. Under company rule and later under the British Raj, Calcutta served as the capital of British-held territories in India until 1911. In that year, after assessing its geographical location, combined with growing nationalism in Bengal (Calcutta became the centre for the Indian independence movement), the British moved the capital to the relatively more centrally located New Delhi.

Following independence in 1947, Kolkata, which was once the premier centre of Indian commerce, culture, and politics, suffered many decades of political violence and economic stagnation before it rebounded. A demographically diverse global city, the culture of Kolkata features idiosyncrasies that include distinctively close-knit neighbourhoods (paras) and freestyle conversations (adda). Kolkata is home to eastern India's film industry, known as Tollywood, and cultural institutions, such as the Academy of Fine Arts, the Victoria Memorial, the Asiatic Society, the Indian Museum, and the National Library of India. Among scientific institutions, Kolkata hosts the Agri Horticultural Society of India, the Geological Survey of India, the Botanical Survey of India, the Calcutta Mathematical Society, the Indian Science Congress Association, the Zoological Survey of India, the Institution of Engineers, the Anthropological Survey of India and the Indian Public Health Association. Four Nobel laureates and two Nobel Memorial Prize winners are associated with the city. Though home to major cricketing venues and franchises, Kolkata stands out in India for being the country's centre of association football and also having strong culture in other sports less widespread elsewhere.

The Imperial Japanese Army Air Service (IJAAS) or Imperial Japanese Army Air Force (IJAAF; Japanese: 大日本帝國陸軍航空部隊, romanized: Dainippon Teikoku Rikugun Kōkūbutai, lit. 'Greater Japan Empire Army Air Corps') was the aviation force of the Imperial Japanese Army (IJA). Just as the IJA in general was modeled mainly on the German Army, the IJAAS initially developed along similar lines to the Imperial German Army Aviation; its primary mission was to provide tactical close air support for ground forces, as well as a limited air interdiction capability. The IJAAS also provided aerial reconnaissance to other branches of the IJA. While the IJAAS engaged in strategic bombing of cities such as Shanghai, Nanking, Canton, Chongqing, Rangoon, and Mandalay, this was not the primary mission of the IJAAS, and it lacked a heavy bomber force.

It did not usually control artillery spotter/observer aircraft; artillery battalions controlled the light aircraft and balloons that operated in these roles.

The Imperial Japanese Navy Air Service was responsible for long-range bomber and attack aircraft, as well as strategic air defense. It was not until the later stages of the Pacific War that the two air arms attempted to integrate the air defense of the home islands.