"Our aim was to take the pitches out of the equation. You have to take 20 wickets, whether it's Johannesburg, Mumbai, Delhi, Auckland or even Melbourne where we won [against Australia]. How do you do that? For that, you need fast bowlers, spinners, a complete bowling unit."

Those were Ravi Shastri's words after India rolled over South Africa in the three-Test series at home last month. While the batsmen racked up big hundreds in the series, the performance of the bowlers was, arguably, even more impressive: on pitches that weren't loaded in favour of them, India's seamers and spinners comprehensively outbowled their South African counterparts. In fact, never since their readmission have South Africa's pacers been outbowled by the opposition fast bowlers as comprehensively as they were in this series.

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India's bowling displays in these three Tests were only the latest in what has been consistently incisive performances over the last few years, no matter what the conditions. The bowling is largely the reason why India have a win-loss ratio of 3:1 and a win percentage of 61% since Virat Kohli took over as captain - both are third-best among the 27 captains who have led in at least 40 Tests. Among Indian captains, Kohli's numbers are well clear of everyone else's.

Kohli has had at his command an attack that has great skill, variety and depth, and the numbers tell the story: apart from his debut series as captain in Australia in 2014-15, Kohli has led the team in 14 series (excluding one-off Tests); in all of them except one, the bowlers have conceded fewer than 30 runs per wicket. The average of 24.56 at home isn't a surprise, but they have also averaged 23.49 in South Africa, 25 in Australia, and 29.81 in England.

Overall, India have conceded 26.11 runs per wicket in the 51 Tests that Kohli has captained in, which makes them one of the top bowling teams that any captain has ever had. Among the captains who have led in at least 40 Tests, only three have had bowling units with better averages over their entire captaincy stints. One of them is England's Peter May, who led in the 1950s and early 1960s, when uncovered pitches were the norm and scores were generally a bit lower. The other two teams with lower averages than Kohli's India are the South African team led by Hansie Cronje, and Viv Richards' West Indies; unlike this Indian team, both those bowling attacks were dominated by pace.

Kohli's India are also among the top three teams in terms of wickets taken per Test. They average 18, only marginally lower than the 18.1 achieved by the Australian teams under Ricky Ponting and Steve Waugh. Of the 19 Tests captained by Kohli since the start of 2018, India have taken 20 wickets on 16 occasions. [This excludes the Afghanistan Test, when Ajinkya Rahane was captain.] In the grid above, this Indian team sits comfortably with six others who take 17 or more wickets per Test at averages below 28: the Australian teams led by Waugh and Mark Taylor; West Indies under Clive Lloyd and Richards, May's England and Cronje's South Africa.

Unlike some of those other teams that have relied almost exclusively on pace, though, this Indian line-up has excellence in both pace and spin, something that has rarely been achieved by bowling units over the years. May's England had an outstanding pace-spin combination - how does a line-up of Fred Trueman, Brian Statham, Jim Laker and Tony Lock sound to you? - while Shane Warne's presence in an otherwise pace-heavy line-up made the Australian attacks under Taylor, Waugh and Ponting balanced and extremely lethal.

Andrew Strauss' England had that balance as well, when Graeme Swann was in his pomp, but few other bowling line-ups have been similarly blessed. Misbah-ul-Haq was able to rely to Yasir Shah and Saeed Ajmal, but he didn't have a particularly strong pace attack to call upon.

In Kohli's Indian bowling line-up, the fast bowlers take 47% of the wickets, at an average of 26.79, while the spinners contribute 53%, averaging 25.02. Those are almost perfect numbers for a bowling unit, suggesting shared responsibilities of bowling duties between pace and spin, with both equally capable of taking wickets. In fact, Kohli is among only four captains in this list, for whom the pace-spin wickets distribution lies between a 70-30 to 40-60 percentage ratio, and both fast bowlers and spinners average under 30. The other captains who have lucky enough to have such varied and efficient bowling attacks are May, Taylor and Waugh.

The scatter plots for pace attack of each captain maps the averages against the percentage of wickets taken. Richards is in the extreme top right: in the 50 Tests he captained, West Indies' fast bowlers took 95.5% of the total bowler wickets, and averaged 22.89 runs per wicket. In Lloyd's era, fast bowlers contributed 88.8% of the bowler wickets, and averaged 24.93. For Cronje, the percentage contribution was 84.2. At the other extreme is MAK Pataudi, who led a spin-dominated Indian attack: fast bowlers contributed only 19% of the total bowler wickets. Kohli's India is relatively low in percentage terms because of the number of home games, but the average is excellent.

The spin scatter plot has far fewer teams in the sub-30-average region, which is to be expected. There are only four names there - May, Kohli, Taylor and Waugh. However, there are many other teams whose spinners average only marginally above 30, including Misbah's Pakistan, the Indian teams under Sourav Ganguly and Mohammad Azharuddin, Ponting's Australia and Strauss' England. The two dots that stand out from the rest are again Pataudi's India - where 81% of the bowler dismissals were by spinners - and Richards' West Indies, where spinners took 4.5% of the wickets at an average of nearly 55.

The strategic skills of all captains look much better when they have a bowling attack that can apply sustained and relentless pressure on opposition batsmen. Kohli has been blessed with such a line-up: in his stint as captain so far, there are five bowlers with 50-plus wickets at sub-30 averages - R Ashwin, Ravindra Jadeja, Mohammed Shami, Ishant Sharma and Jasprit Bumrah. Umesh Yadav just misses the mark, averaging 32.51 for his 79 wickets under Kohli.

Among the 27 captains who have led in at least 40 Tests, only nine have had at least five such bowlers. Among them, only three - May, Ponting and Kohli - have had more than one spinner in that list. Lloyd, Richards and Michael Vaughan are in this list of nine, but with all-pace line-ups.

Out of the five bowlers who average below 30 in Kohli's India, three of them - Ashwin, Jadeja and Bumrah - average less than 25. Only seven captains have had the luxury of at least three bowlers taking 50-plus wickets and averaging below 25.

All of this indicates that this attack is not only the best that India have ever had - by a distance - but also one of the best that any captain has had the privilege of leading. That said, though, Kohli's India have still lost Test series in England and South Africa, and 37 of their 51 Tests have either been in Asia or in the West Indies, which have been easier venues for India's bowlers in the last few years.

However, it's clear that this balanced bowling attack has given the Indian team an edge it has seldom had, given that India have traditionally been known as a batting and spin powerhouse. The presence of a solid pace attack has made India competitive overseas, and has given them opportunities to consistently notch up wins when playing away from home. In home conditions, India have always been tough to beat, but armed with this bowling attack, they have become almost unbeatable.

With inputs from Shiva Jayaraman