I think that Partition was probably the most important event in Indian History.  On one hand, that sounds really elemental because India only comes into existence in 1947 as a result of the partitioning up of the Indian Subcontinent into different nations.  Partition became the term that involved how the subcontinent was going to be divided after the British left.  It also refers to the creation of multiple states from this process.  The implications of Partition became profound on India in the riots that ensued, the mass migration of millions of people across borders, and the idea that something as complex and intricate as the Indian subcontinent and cultures that have intermingled for thousands of years can be arbitrarily divided through political borders have cast their shadows on India, Pakistan, Bangladesh, and Sri Lanka today.  The current challenges for India in the Jammu- Kashmir region goes back to Partition, and the belief that the Kashmiris would be better in India without their consent.  The intensity between Pakistan and India was forged during Partition and is still felt today, with examples such as the 26/11 bombings in Mumbai and the Indian participation in the marginalization of Pakistan as a result of the Bin Laden killing.  Partition is a shadow on the modern subcontinent, and its significance is gargantuan.