Partition of India
The Partition of India refers to the regions of northwestern India and parts of eastern India being partitioned away from the country in order to create Pakistan. It was caused by the British support for the Muslim League, though it was opposed my many politicians, political parties and religious groups. The Partition of India led to the killing and forced conversion of around 4.75 million Hindus.
Before the British
For Hundreds of years, India had been occupied by tyrannical Islamic Empires. These invaders indulged in mass killing, rape and destruction of Hindu temples. The Hindus who were not killed suffered heavy taxation(Jizya Tax), which resulted in many poor people having to convert to Islam. 
In the 1700's, an Islamic scholar by the name of Shah Waliullah Dehlavi, declared India Dar-ul Harb. Dehlavi approached the Emir of Afghanistan, Ahmad Shah Abdali in the year of 1761, requesting him to invade India. He also convinced the Muslim Nawabs to support Abdali's invasion.
Additionally, 34 Ulemas(councils of Islamic scholars) issued fatwas declaring India as Dar ul Harb.
However despite Islamic extremist bigots like Dehlavi, the vast majority of Indian Muslims considered themselves as culturally Indian and not Arab. For instance, Wajid Ali Shah of the Kingdom of Awadh, was well known for composing and singing Radha Kanhaiyya Ka Kissa(Tale of Radha and Krishna). Additionally, there was Mir Taqui Mir, an Urdu poet who wrote, "What do you ask Mir of his faith and religion? Since long he as put on janew(sacred thread of Hindus), sit in the temple and has given up Islam." 
Under British Rule
It was under British rule in India that the idea of dividing India on religious lines came about. The earliest recorded reference to dividing India goes back to 1843. In a speech to the British Parliament, Thomas Macaulay, who introduced English education in India, offered a suggestion on how the British government should deal with India Hindu majority versus the Muslim minority. He stated that Britain should, "take no part in the disputes between Mahometans and idolaters. But, if our government does take a part, there can be no doubt that Mahometanism is entitled to the preference.
Wali Khan, the son of Abdul Ghaffar Khan, wrote a book titled "Untold Story of Partition". He wrote, "The British are manipulative people, experienced in ways of modern sabotage. They seriously set out to find the best means for establishing control over the numerous small kingdoms and millions of individuals....Unity among Indians spelt disaster for the British, which they wanted to avoid at all costs."
After the 1857 Indian War of Independence, the British confiscated and gifted lands of Hindus to Muslims who were loyal to the British. The British also guaranteed non-interference in Muslim religious places.
In 1905, the British split Bengal by separating Muslim eastern areas from Hindu western areas. The Muslims then called for Jihad with the goal of converting Eastern Bengal into Dar-ul-Islam(Muslim controlled land). With the support of the British officers and magistrates, the Muslims attacked Hindus. When Hindus led by Rabindranath Tagore. led a protest against the partition of Bengal, the 1st Lieutenant Governor of the new province, Sir Joseph Bampfylde Fuller, treated this as treason and let the police loose on the Hindus. On December 12, 1911, due to widespread unpopularity, the partition of Bengal was removed.
The British introduced the Minto Morley reforms in the year of 1909, giving a separate electorate for Muslims. It promoted Anti-Hindu and Islamic separatist leadership.
The British then proceeded to look for Indian Muslim collaborators. On November 2, 1921, Mohammad Shafi, a member of the Viceroy's Executive Council, submitted a memo which proposed that to undermine growing religious unity in India, it was important to separate the Muslims from it. The memo also proposed an Anglo-Mohammedan Union that would operate in the interest of the British Empire.
On September 21, 1922, the Viceroy, Reading, wrote to Birkenhead, the Secretary of State for India: "I have sent you a telegram, which will show you how near we have been to a complete break between Muslims and Hindus. I have been giving the greatest attention to this possibility, and I have the greatest assistance from Shafi in my council, who is a highly respected Mohammadan."
The British succeeded in turning away many Muslims from the Indian Independence Cause. In 1939, Nawab Ismail Khan, a Muslim League member from UP, wrote to the British that "a democratic system at the centre is not acceptable to the Muslim community. Another Muslim League member also sent a telegram to the Viceroy saying,"The Muslims have no differences with Great Britain....They wanted Britain to stay and they are now growing popular with the Muslim community."
Concept of "Pakistan"
By the 1930's, the concept of "Pakistan", which was coined by Islamic Supremacist Chaudhry Rehmat Ali, started to gain ground among the Muslim League. In 1939, Viceroy of India, Lord Linlithgow, worked with the Muslim League to counter the Indian National Congress' demand for full Indian Independence from British rule and to come up with an alternative. Linlithgow told Jinnah in September 1939 that if the Muslim League regarded it as unsuitable for India to become a dominion within the Commonwealth, 'then the escape from the impasse is Partition'. 
Plotting the Creation of Pakistan
After WW2, the British were not able to hold on to India any longer. The British wanted to maintain their imperialist influence over Iran, Iraq, Kuwait, the UAE, Bahrain and Qatar, so they decided to create Pakistan for the purpose of retaining a foothold in the NWFP and Balochistan. However Britain encountered issues doing this as the NWFP had elected a government from the Indian national Congress and not from the Muslim League. Therefore, Louis Mountbatten, with the help of his wife Edwina, talked Jawaharlal Nehru into agreeing to a referendum in the NWFP. Although it is claimed that 99% of the votes were in favor of Pakistan, there was widespread fraud and rigging done during the referendum. Ghaffar Khan said that bogus votes were polled in favor of Pakistan. 
Anti-Hindu Riots/Pogroms before and after the Partition of India
- See also: Great Calcutta Killing
On August 16, 1946, Muhammad Ali Jinnah proclaimed "Direct Action Day". Soon after, more than 4,000 Hindus were massacred at the hands of Muslim mobs in the city of Calcutta.
On October 10, 1946, Muslim mobs massacred 5,000 Hindus in the Noakhali region of Bengal and raped hundreds of women. Many thousands more were also forced to concert to Islam. On the island of Sandwip, gasoline was imported from the mainland to burn down houses owned by Hindus.
In March of 1947, incited by the Pir of Golra Sharif, Muslim League mobs attacked Hindus and Sikhs in villages of Multan, Rawalpindi, Campbellpur, and Jhelum Sargodha.
Direct British Involvement in Anti-Hindu Pogroms
In addition to the British providing funding to the Muslim League and giving them vocal support in their goal to create Pakistan, they also had a direct hand in Anti-Hindu Pogroms. Former Indian Army chief V.K Singh, in his book "Leadership in the Indian Army" has mentioned how British officers and troops were encouraging riots. He writes: "Once the decision to divide the country was taken it was clear there would be large-scale movement of people in Punjab. To supervise their move and prevent violence, a Boundary Force, based on a division created under the command of Major General T.W Rees with the headquarters at Lahore."
General Kodandera S. Thimmaya, was appointed commander of 5 Brigade, located at Amritsar, which was part of this force. Thimmaya "found that the British officers were indifferent and not very keen to prevent disturbances". Lieutenant General Thakur Nathu Singh had a similar experience with British officers. When India became Independent, Nathu Singh was in charge of the Derajat Force at Dera Ismail Khan in NWFP. "He was shocked at the behavior of some British officers of the civil service, who were encouraging the local Muslim population to threaten Hindus and force them to migrate to India. He tried his best to check this and brought it to the attention of the political leaders, who pleaded helplessness."