West Indies post 195-4 against India in T20 World Cup do-or-die clash
Jason Holder and Rovman Powell smashed 70 off the last five overs to help their side set defending champions India a challenging 196 to stay alive in the tournament.
The winners at Eden Gardens will move on to a semi-final against England in Mumbai on Thursday -- the losers will go home.
The West Indies sprang a surprise at the top of the order, promoting Test captain Roston Chase to open alongside T20 skipper Shai Hope.
That enabled them to bring in an extra spinner, Akeal Hosein, with regular opener Brandon King left out.
In their defeat to South Africa last week the West Indies slumped to 83-7 but the new-look opening partnership was more assured.
Spinner Varun Chakravarthy got the first breakthrough, bowling Hope for 32 after a stand of 68 to a deafening roar from the 67,000 packed into Eden Gardens.
Shimron Hetmyer raced to 27 off 12 balls before falling to the faintest of edges off Jasprit Bumrah to make it 102-2.
Two balls later it was 103-3 when Bumrah induced Chase, on 40, to chip a slower ball to India captain Suryakumar Yadav.
After Sherfane Rutherford fell cheaply, Powell and Holder launched their brutal late assault in an unbroken stand of 76 for the fifth wicket.
Powell finished on 34 not out from 19 balls with two sixes and tree fours while Holder was unbeaten on 37 off 22 balls with three sixes and two fours.
It could have been better for India but they dropped three regulation catches in a sloppy fielding display, including Chase when he had made just 15.
South Africa, the only unbeaten side in the tournament, beat Zimbabwe by five wickets earlier on Sunday and will face New Zealand in Kolkata in the first semi-final on Wednesday.
The final is in Ahmedabad next Sunday.