How did the Eastern part of the region of Bengal end up with a Muslim majority?

Because of the History of India.Bangladesh came into existence in the year 1971. Before 1971, it was East Pakistan. And before 1947 it was a part of India, Bengal to be precise.When India was partitioned on the basis of Hindu-Muslim separation, There were two major areas which had Muslim concentration more than Hindus.Since both East Pakistan (presently Bangladesh) and West Pakistan (presently Pakistan) were very far from each other, therefore, two separate areas were allotted to the nation made on Islamic grounds (Pakistan).At the time of independence in 1947 India had a large population of both hindus and Muslim. Due the difference created by the Britishers during their reign, communal riots became almost regular.If the Muslims of Bengal had to migrate from Bengal area to the Punjab area (Pakistan), the whole travelling route would have been communal in nature as in those times communal riots were at their peak.Bangladesh has a large Muslim majority because India used to have a large Muslim majority before independence, and still continues to have a large Muslim population.See India's map before Independence: (Image from Google Images)

Indian muslims accepted islam through sufi efforts and arab traders but there might be few rare cases of force conversion but they are very insignicant. Most of the part there was no force conversion but the conversion happened peacefully through traders and sufi saints tireless efforts. Now you would not want to agree with this but then few questions arises such as... which muslim army went to maldives mauritius in the indian sea? and to malaysia indonesia the largest muslim nation by population? and to part of philipines n china where there r muslim majority states? Muslims ruled india for 1000s years from their throne in delhi but all the surrounding areas are hindu majority inckuding delhi when it should be full of muslims and should be a muslim strong hold? Surprise!!!!!!! All these inreturn reject the force conversion myth of india which the critics of islam would love to bring up on all occasions both knowingly n unknowingly! Still not satisfy? I invite u to check the map and analyse the muslims concentrated areas of india or british india if pak bangladesh is to be included. You will find states like UP bihar assam west bengal kerala the island lakshwadeep(96 percent muslims) Maharashtra gujarat have large muslim population. Point to be noted most of these states are very far away from the main seat of muslim power in delhi. Infact the immediate next door states punjab rajhasthan himachal utrakhand and surrounding areas and central areas of india generally has the lowest population of muslims and states closer to sea are populated by muslims. The people of these areas were introuduced to islam by arab traders same way as the above countries.  Pakistan and remaining indian states which are far from sea were introduced to islam mostly by sufi saints over centuries during the muslim rule. Point to be noted pakistan is mostly a sufi muslim nation. Sind was attacked by the arabs because the unjust hindu ruler attacked the sea trade routes of the arabs and also imprisoned muslims traveling from sri lanka to arab world wrote letters for help. Its well recorded in history that the sujects of the ruler of sind buddist and hindus actually offer the arabs a helping hand by joining their army against the unjust hindu ruler and toppled him. Some hard questions Why millions of people from martial community of the subcontinent accepted islam e.g. rajputs jats gujars when millions of dalits which are considered weak and helpless in india remained hindus? Why delhi the muslim seat of power for centuries and surrounding states are hindu? why are villages towns cities near the shore are highly muslim concentrated? Which army went to the indian island lakshawadeep where 96 percent are muslims and other countries maldives mauritious malaysia indonesia and part of philipines? this is the hardest one WHY THE SO CALLED FORCED CONVERTED MUSLIMS FROM PAK TO BENGLADESH DIDNT GO BACK TO HINDUISM? WHATS STOPPING THEM NOW?THERE IS NO MUSLIM ARMY WITH SWORDS STANDING OVER THEIR HEADS!!! SPECIALLY THE INDIAN MUSLIMS NOW THAT THEY LIVE IN A HINDU MAJORITY COUNTRY, SO WHATS STOPPING THEM?PAKISTAN???

We can make few observation and based on which we can make a call !!. You will notice the muslims in east bengal i.e bangladesh do share the same culture, language, food and even dress code i.e saree etc etc with west bengal which clearly showcases that at one point of time all had same ancestors as well as same religion in the past and those religions could be buddhism and hinduism. (yes physique and looks r similar too) There is also a claim that buddhism was very common during those days (and mostly in the eastern areas) but this is very unlikely in places where hinduism already existed. Buddhism actually coexisted side by side with hinduism and that too in the form of schools (monestery) mosly and it was mostly made to spread outside the areas where hinduism didnt exist. Those areas include tibet, parts of afghanistan, central asia, western pakistan etc.  since buddishim is a sort of lighter format of hinduism and quite often can be practiced together as buddhism and hinduism .... thats why we sometimes see ganesha idols reaching far east, obviously buddish monks (who were offcourse hindus) took it with them since they believed in hinduism as well.... ( we all know dharmic religions [hinduism, sikhisim, jainism, buddhism] always have huge overlaps )No doubt the rulers like pala dynasty were buddhist whose domain spread from bengal to afghanstan but mainly buddism spread in tibet , afghanistan, srilanka during that time..otherwise we would have seen deep remains / influence  of buddhism in bengal which isnt the case...so basically buddhism was for newer regions where hinduism wasnt widespread ... Also we see  from 13th century bengal came under islamic rule under bengal sultans...and that was the time when islamization started.. We know generally 3 ways people convert - either via violence or via bribe or volutarily (if someone is very much influenced by a new religion)We all know that islam is totally different from hinduism and its very unlikely that anyone would convert volutarily..But from past stories we have heard that during those days society was divided into upper and lower. There were also saying that if some muslim touches anyone the society would boycott that guy... The population of lower class was always much higher than upper and they do had a loose grip over their original religion. During that time since the rulers were muslim sultans they exploited this class divide and bribe the poor for a better life in the form of free benefits and class obsession. This is very similar to what christian missionary do in india (bribing people to convert on return of free benefit/jobs/ social recognision/identity etc). Yes such thing did happend for next 500 yrs (islamic empre + mughals) and 500 yrs is a long period and we all know that islamist do not endorse family planning (also they wish that all world be muslims one day) and hence the multiplication rate was much higher in the east compared to western bengal....also multiplication in last 200-300 yrs must be highest (Eg: 1872, 53% of the people in what is now Bangladesh were Hindus. In 1900, it was 32.7%, and by 1947 etc etc from some source). .. thats the reason we see alot of muslims in east and majority of them are due to faster multiplication. ...so u see at some point hindus were in majority, but i would say all were hindus at some point of time .... so its like a fixed deposit like money doubles in 7 years but here as humans population doubles in hundred/2 hundred year, and that all happened in islamic period...Yes conversion did happend in large numbers there but the real population which we see today is due to faster multiplication....yes only positive thing which i can see here is they follow the same culture with some urdu words being introduced , the conversion doesnt seem to be forceful. Yes sufis did played a role for easy transition as they didnt enforced them to follow arabian lifestyle, thats why the culture is same except religion.... yes some forceful conversion did happend but that was during the later years and still happening. Also majority of names which lie in bangaldesh are mostly hindu and sankritised too whcih proves these people mostly were predominently hindus not buddhist in the past.Also sad part is the area is still the poorest in the world (so called bangladesh) with voilence and instability  inspite of ditching their ancestorial religion..  There may be several gramatical / spelling errors above...do excuse .dont have time to revise!  

It was the tyranny of the Brahamins of Hindu community, who always use to hate not only the Muslims but even the lower groups of Hindus.  On the other  hand Muslim religion created by a very intelligent man Muhammad Hazrat so that the religion expands,  so that no body is denied to enter to the religion at ease, apart from multiple marriage system due to which the population has increased from 4 core to 17 cores, Where thus neglected Hindus of East Bengal had taken up Muslim religion. Now after partition of Bengal, what had happen, west Bengal was kept for Hindus and East Bengal was kept for Muslims in 1947, but again in 1950, Nehru made Nehru-Liaqluate Ali Pact and bring back the Muslims of East Pakistan, how intelligent our PM is. It is the Hindus of India , who had pushed the present west Bengal to be a Muslim state, otherwise, the Hindu leaders should have protected the rights of Hindus in west Bengal by giving them the absolute right of votes in west Bengal and no voting rights for the Muslims as they got East Bengal, by partition but Gandhi, Nehru or Petal did not done it. Therefore Indian should not blame the Bengali Hindus of Bengal, who are now , under the threat of Muslims and a new thinking is in their front as it was once due the tyranny of Brshamin. It is the Indians  who are compelling the Hindu Bengalis to get converted to Muslims. Your policy, the policy of Delhi Government, right from the beginning destroying the Hindus, just to get rid of Hindu leaders. CR Das died, Netaji fled away, you did not stop rioting rather agreed with Jinnah to divide Bengal by rioting. You did nothing  while millions of Hindus in East Pakistan, were being, anf now also they are in threat, the secular Bangladesh has now changed to Islamic Bangladesh, you India had brought independence to Bangladesh but you have no control over Bangladesh, where is the future of Hindus of Bangladesh, other than converted to Muslims, the same is also you have created in west Bengal, that is why even Mamota have no alternative other than Muslim favour, not the question  of ordinary people.

Balaji's Answer explains alot about How majority of Bengalis became muslim . But there is a specific reason why this only happened in Bengal which is far away from the khyber pass .From where Muslims invaded India . Punjabis Pashtun Balochis and Sindhis became Muslims due to their proximity to Iran but why Bengal and also why only eastern part of Bengal . I have my opinion on this . West Bengal had been part of Indian history for a long time . I believe that Entire bengal used to be huge forest as it is a very fertile land .Full of vegetation . Thus before 3000-2000 years only Adivasis resided in that area . After Maurya and Gupta dynasty was founded in Patana(Patliputra) . Hindus and Buddhists started cutting down forests in Bengal and started settling there . But still huge eastern part was not incorporated . So most of them still stayed Animists . As time went on people kept cutting forests further east making Western parts of Bengal completely hindu and buddhist . But eastern part stayed adivasis . So obviously they must not have been treated well by civilized west bengalis . As Mughals arrived in that are 600 years ago . Those adivasis finally found a religion which would allow them to become equals or even superior than Hindus . Thus they quickly adopted it . And majority became Muslim ! This is the only logical reason . Otherwise low caste hindus were everywhere in india all the time ! Why only Bengalis would accept Islam so quickly and completely because they were adivasis who were not even considered hindus !  So Bangladesh was never hindu to begin with it was always majority adivasi and later on Muslim !

According to Encyclopedia Britannica (1974), as late as 1872, Hindus outnumbered Muslims in Bengal (18 million to 16 million)The balance began to tilt towards the Muslims from the 1890s, which is attributed primarily to significant activity of the Sufis. Other reasons for the change include migration on Muslims from other parts of India and outside India into Bengal and a higher birth rate attributed to Hindu widows not being allowed to marry.  I have also read that a major movement called Faraizi movement took place over several decades in the 1800s, which caught the imagination of the peasantry in Bengal. The movement was concentrated in the eastern districts of Bengal, e.g. Dhaka, Barisal, Faridpur, Mymensingh and Comilla. Hence, perhaps the higher percentage of Muslims in east Bengal, and also tilting the scale towards the Muslims in Bengal as a whole.

Before the partition of India, Pakistan and Bangladesh were also a part of India and Muslim population were found in all three regions.During the British rule in India The decision to effect the Partition of Bengal(currently West Bengal, a state in India.) was announced in July 1905 by the Viceroy of India, Lord Curzon. The partition took place on 16 October 1905 and separated the largely Muslim eastern areas(Bangladesh region) from the largely Hindu western areas.So at the Time of partition of India all muslim people who did not want to stay in India and were living in the eastern region of India moved to this eastern region of bengal also known as "Eastern Pakistan"The borders of modern Bangladesh were established with the partition of Bengal and India in August 1947, when the region became East Pakistan as a part of the newly formed State of Pakistan.It was separated from West Pakistan by 1,600 km (994 mi) of Indian territory. Due to political exclusion, ethnic and linguistic discrimination, as well as economic neglect by the politically dominant western-wing, popular agitation and civil disobedience led to the war of independence in 1971.

You missed thr trick where you failed to notice that INDIA as a country is the largest muslim populated one with over 250 million muslims. The route of the Islamic preachers starting from the 7th century till the 17th century has been through Pakistan towards the bengal delta concentrating on northern parts of India. So the idea of Bangladesh being isolated from other Muslim nations is misinformed.

I have a theory on this but I don't have any proof. West Bengal had more rich and influential upper class Hindus as compared to the East Bengal. Now under the circumstances of conversions; either by force or for some benefits (tax benefits etc.) or otherwise, the poor and the uneducated can be easily coaxed but the rich and educated can take a stand. Further Hindu caste system is notorious for its ill treating of lower caste Hindus.  These people when given a choice : 1) living a miserable life within their religion and community or 2) A respectable life by changing their religion and community would most likely change their religion then the upper caste rich Hindus. Also somebody has mentioned that the eastern region had already been under Buddhism which later converted to Islam; it further supports my argument.