India has been wracked by terror attacks by a variety of assailants since gaining independence from Britain in 1947.
Its population of 1.2 billion is comprised of numerous _ and in some cases competing _ ethnicities, and the divide between the rising middle class and those still mired deep in poverty has added to tensions.
The South Asia Terrorism Portal, which tracks terror attacks in the region, lists more than 170 terror, extremist or insurgent groups in the country.
India has also fought three wars with archrival Pakistan and accuses its neighbor of actively supporting terror attacks by Pakistani-based militants on Indian soil.
Though India made significant investments in its security forces after the 2008 Mumbai attacks, its police forces remain poorly trained, undersupplied and tainted by corruption.
Mumbai, India's commercial and entertainment hub, is crowded with 18 million people, billionaire businessmen and Bollywood superstars and has repeatedly been targeted by terror groups seeking to reap maximum exposure from their attacks.
The 2008 attacks by 10 Pakistan-based militants targeted India's busiest train station, a Jewish center and two luxury hotels in the city and left 166 people dead.
Since then, the city had escaped further attack, until three coordinated bombings Wednesday night killed 17 people.