India sealed their fourth straight victory of the T20 World Cup as they defeated Australia in the final group game on Sunday. MS Dhoni's men take the top spot in Group 2 with eight points from four games and have made it to the last four of the tournament with ease.

India will face South Africa in the semi-finals, as the Proteas are guaranteed to finish in second place in Group 1. The men in green have Dale Steyn and AB De Villiers to call upon, but the Indians will be confident of victory.

The turnaround by Dhoni and his men is truly remarkable, given India's poor form during the Asia Cup in the lead-up to the tournament. Having come third in the preamble, India have looked a team transformed so far in the World Cup - in fact they have been peerless in all three disciplines.

But how have they turned it around? How can a team which looked so ordinary in the warm-ups become so lethal when the real thing starts?

Here, IBTimes UK looks at key areas which have been vital in India's success so far in the ongoing tournament.

1. Spin attack

Dhoni has built his attack around spin, using Ravindra Jadeja, Ravichandran Ashwin and Amit Mishra as attacking options with the support of pacers Bhuvneshwar Kumar and Mohammed Shami.

Jadeja, Ashwin and Mishra have shared 21 wickets in the four group stage fixtures. The latter was hugely impressive against Pakistan and West Indies, bagging the Man of The Match award in both occasions.

Ashwin's 2-15 against Bangladesh and 4-11 during India's win over Australia saw him get the Man of The Match in the last two matches. The trio can also be supported by part-time spinners like Yuvraj Singh, Suresh Raina and Rohit Sharma - no other team in the tournament has the wealth of slow-bowling options at Dhoni's disposal.

All four teams from Group 2 have struggled against Indian spinners. The South Africans will have to hammer Dhoni's army of twirlers if they have to stand a chance of progressing to the final of the T20 World Cup.

2. Strong Batting Lineup

India have a very strong batting lineup, which has helped them chase the required target comfortably in the three of the four Super 10 fixtures. India lost three wickets in the first two matches, while losing only two against Bangladesh during the third T20 tie. Although seven wickets were shed against Australia, three of those came off the last nine balls of the innings.

Rohit Sharma and Virat Kohli have been the key contributors to India's batting operation, with 147 and 170 runs respectively so far. Yuvraj Singh was poor with the bat during the first two games, but he came good against Australia with a brilliant knock of 60 from 43 deliveries, which included four 6s and five 4s.

Shikhar Dhawan is capable of taking the game away from the opposition with his range of strokes at the top of the order. Lower down, India can draw upon the power of Raina, Dhoni and Jadeja, who dovetail perfectly at the end of the innings.

3. Squad depth

India have very strong backup options, a strength clearly visible during the fourth Super 10 fixture against Australia. Dhawan was replaced by Ajinkya Rahane, who put on a vital stand of 40 runs for the first wicket, while Shami was given a rest and Mohit Sharma came in to claim the crucial wicket of Shane Watson.

The backup players are also performing for India, creating the perfect selection headache for captain and coach.

4. Tactics

Dhoni has implemented a strategy perfectly attuned to the conditions, bowling first, keeping it tight with spin and fielding like tigers. India haven't gone for too many shies at the stumps, happy to keep the batsman to one rather than risking overthrows.

India have not used an express pacerman, but have instead relied on spinners and medium-pacers to do the job so far in the T20 World Cup. Taking the pace off the ball has worked perfectly so far, and there's certainly no reason to change the strategy from here on in.

5. Dhoni factor

Dhoni was missing during the Asia Cup as Virat Kohli. However the iconic wicket-keeper's return to the squad has lifted players and fans alike.

Dhoni has already guided India to T20 triumph during the first World Cup in 2007. He also played a crucial role in India's success during the ODI World Cup in 2011, as well as the win in the Champions Trophy in England last year.

If India win this edition of the T20 World Cup, they will become the first team to hold the ODI World Cup, Champions Trophy and T20 World Cup title at the same time - a fitting testament to Dhoni's leadership skills and force of personality.