New Zealand's left-and-right pace duo, Trent Boult and Tim Southee, have led the attack for over eight years now, taking 616 wickets in the 118 internationals in which they have appeared together. In this interview (put together from separate conversations each bowler had with different ESPNcricinfo staffers) they talk about what makes them click so well.

On nerves when opening the bowling

Trent Boult: It's actually quite different between one-dayers and Tests. In a Test, I can find myself being quite nervous, especially if you win the toss and bowl. It's almost a bit of pressure on the bowlers to be on the mark and to take a couple of wickets and set the Test match up nicely.

With the white ball, you have to be on the ball from the start. For some reason, that kicks into your head and you just get into it. It's a lot less room for error. I'm just trying to run in and be as aggressive as I can and put it in the right area.

Tim Southee: I think there's nervous energy, excitement, any time you are about to play a game. I enjoy the nerves and the excitement, but most of the time it is probably more leading into the game. By the time you go into the ground and warm up, it settles the nerves.

I think [the goal when bowling with the new ball is] to be aggressive, look to take wickets. Fulfil your role for the team in the situation of the match. It depends on how the team is going, and how you are feeling on the day. Conditions also come into play a lot, so it varies.

Boult: Test cricket's my favourite format. Maybe there's a lot more nerves there for that reason. It just etches itself into history. Once those nerves are out of the way and I'm into my rhythm I definitely feel at home.

On swing

Boult: When the ball is swinging, I feel that's my biggest threat - trying to pitch the ball up and get it moving as much as I can, and bring that bad judgement out of the batsman. That was the learning curve when I was a bit younger - finding how much the ball swung. Now it's all about length. How full can I bowl it without being driven or overpitching? How can I swing it from a shorter length? It's finding that natural length where you bring batsmen forward, and then I feel I can get the best out of the late swing.

It's a lot to do with the overhead conditions. In New Zealand it can swing nicely, but it's also windy, which pretty much eliminates the swing straight away.

Southee: I am a swing bowler, so I do prefer it when it is swinging. Of late, in the last few years, it hasn't really swung, especially in white-ball cricket, so it is about finding other ways to still take wickets, and not relying on it just swinging. When it does swing, you become even more dangerous.

Boult: It's always an evolving thing for me. I swing the ball really nicely in certain conditions, on certain grounds. For some reason I can find myself at the same ground again and find it isn't swinging the way it has previously. It can be a little frustrating. It's been a good learning curve in trying to skim wickets in other ways.

When I was younger, I found that I bowled way too full with the white ball. You can come through the grades and pitch the ball right up, and be able to beat batsmen through the air. I suppose the better the batsman, the quicker they can cash in on that length.

Finding the length is the most important part. The release is quite important as well. For me, it was quite natural to make it come out as an inswinger to a right-hander. I was pretty lucky with that. It takes a lot of confidence to want to push the ball up to some of these players.

"Any time as an outswing bowler you clip the top of the stumps or find the outside edge, it is a nice feeling"

On bowling together

Boult: I'm very lucky to be bowling with one of my best mates - Timmy - who does similar things to what I do, but in the totally opposite direction, which has been proven to give us a lot of good success. It's a good combination and it's been picked up nicely by the rest of the lads as well, with their fielding.

Southee: Having a left- and right-arm certainly does help. It is something different for the batsman. We both swing it. Also, we played a lot of cricket together since the age-group days. We played for the same domestic sides. We have formed a friendship, which goes a long way in understanding each other out in the middle.

Boult: We've been friends since we were 14 or so. It's about learning off each other and recognising when guys are going well or struggling. Timmy's one of the first lads to help me get back into that rhythm. We're very competitive, along with the other bowlers in the group. When we're doing well, that's where a lot of the drive comes from.

Timmy's actually adjusted his game to be in the slip cordon now as well. He's got a good set of hands. I'd love to see the stats on how many catches he's taken off me [16 in Tests]. Left-handers, whom I enjoy bowling against - I set them up to bring them forward and get them caught in the slips, and somehow Timmy seems to be there every time. I feel like I'm a different bowler when we're both out there.

Southee: Understanding each other away from cricket also helps to understand what we are thinking out there and knowing when things are working or not working.

[When Boult is taking wickets], you become a supporting role and try not to go for any runs, and try to pick up wickets as well. It is nice when you both are taking wickets. I think it is all part of a partnership.

Boult: You can bowl one of the best spells in your life and go wicketless. There's been times when Timmy's got six-fors and seven-fors and my role has changed to remaining patient and not leaking runs. It's the importance of bowling from both ends. I know he does it for me. We've played a lot of cricket to know what works well with us. And that's being relentless from both ends, being accurate from both ends, and not allowing the batsman to cash in by rotating the strike and getting easy runs.

On getting the rhythm right

Southee: I think it starts from the run-up. It comes through to what happens in the crease and then when you deliver the ball. The rhythm and smoothness of the run-up is a massive factor for me.

Boult: I try to keep my run-up as natural as possible. I've got to be quick through the crease and quick through my action. When I feel like I'm running in slow and I'm trying to muscle the ball - those are the days when I feel it's not coming out like I want it to.

There's so much cricket in the world and you're playing against certain bowlers numerous times a year. The most foreign of actions - [Lasith] Malinga, Mustafizur [Rahman] - even these guys [you get] quickly familiarised to. [My left-arm] angle opens up a couple of different options, in terms of being able to run the ball away from right-handers and also trying to bring the ball in when its swinging. That's one of my big weapons.

On thinking about sacrificing pace for accuracy

Boult: Not really. You want to have something about you when you're bowling. I wouldn't say I'm an intimidating bowler, physically or with my presence. But I want show the batsman that I'm not going to give him an easy ball to get on top of. When the ball's not swinging and there's not much movement, I think having an extra yard up your sleeve is as important as dropping it down a little bit and trying to swing the ball.

In Test match cricket I find that you can pick your times on when the quicker spells come along. I've driven myself to make sure every spell is stronger than the previous one. Sometimes injuries can be in the back of your mind, but it's about backing your training and technique.

Southee: I guess you get a little bit smarter the older you get. But with extra pace, around mid-to-late 130s, you become more dangerous. It is something that I have been working on, especially this summer. I can hopefully swing it at a good pace. You have played a lot, but you always look for ways to improve and try to play better.

Boult: "When the ball is swinging, I feel that's my biggest threat - trying to pitch it up and get it moving as much as I can. When I was younger, it was about finding how much the ball swung. Now it's all about length" © Getty Images

On bowling idols

Southee: I was always a fan of Glenn McGrath and Curtly Ambrose. McGrath is someone I watched a lot growing up and idolised a lot. In the backyard you imitate a number of people. I have been fortunate to have an action that hasn't changed a lot. It feels natural for my body.

Boult: My idol was Wasim Akram. I used to love the way he used to scurry through the crease so quickly and swing the ball. I tried to imitate him a little bit when I was younger - reverse swing, for sure. Conventional swing as well - like how he used to come around the wicket to the right-handers, straighten the ball in the air, then have it leave them off the pitch. He'd rip their stumps out of the ground. That's something I tried to mimic in the backyard. I've met him a couple of times and he's phenomenal. Amazing skills.

Someone from the more modern era would be Dale Steyn - a guy that can do what he did, and is still doing, is phenomenal. One of the best records in the world. To bowl 150kph and swing the ball. For someone who doesn't have the biggest of statures, he can still play that intimidating role.

Your dream dismissal

Southee: Any time as an outswing bowler you clip the top of the stumps or find the outside edge, it is a nice feeling. Any time you take the wicket of a world-class player, or any batsman for that matter, it is a nice feeling.

"There's been times when Timmy's got six-fors and seven-fors and my role has changed to remaining patient and not leaking runs. It's the importance of bowling from both ends"

Boult: Everyone loves clean-bowling someone. That's at the top of the list. I think when you plan and visualise certain batsmen getting out in certain ways and it actually comes off in the game, that's a great feeling. When you are swinging it in, swinging it in, swinging it in, and then you push one across and he nicks off, that's a good feeling too.

I remember something that went the opposite way, actually. Recently, against Ben Stokes, in a pink-ball Test at Eden Park, the ball swung around really nicely. I think I bowled three or four balls at him. Three of them moved away, and then I turned the ball around and bowled one that nipped back in and bowled him through his gate. To push the off stump out of the ground was one of the more satisfying wickets off late.

On building a knowledge base about pitches

Southee: It is the unique thing about cricket - it is different everywhere you go. The pitch, soil that's used. A number of variables come into play. I guess it is about using your previous experiences. I think you can look at a number of factors and the scouting is done before the series. It improves me as a cricketer. More information is becoming available to players. Use it as much as you can.

Boult: Things can be totally different to what you expect them to be like. We might play in Hamilton and be prepared for a quick, green, bouncy wicket, and then face quite a slow wicket that might turn a bit. Suddenly your plans of bowling a good line and length outside off stump might be exactly what a batsman wants on a slow wicket. It is about adapting.

I've always thought that there's only three or four balls you can bowl as a fast bowler. You can bowl a bouncer, a yorker or a length ball. But there's about 150,000 places you can bowl the ball, and you can change the field. I probably think more now about tactics and how I can set my field to build pressure. How can I build dots and draw the error out of the batsman - that's the more important part to me, rather than sitting down and saying, "I'll bowl this certain length and this certain line."

On reading signs that a batsman is struggling

Boult: Playing and missing, being caught on the crease - those are two clear indicators. If a batsman is leaving me a lot - that's a sign I'm bowling too wide.

Southee: I guess when they don't look as comfortable as they should be. Most of the time when it is swinging, they are not sure whether to leave or play. A comfortable batsman moves their feet relatively well. It is something I look at.

Boult: It's about being patient. Batsmen are so good these days that they can be on your bad balls in a flash. Sometimes they're even hitting your good balls. It's about not getting frustrated if you're not getting wickets. From there, the step further is to ask yourself: are they actually hitting my good balls that are going where I'm trying to bowl them? If they are, that's all you can do, in a way. If they're not, you've got to tighten up those lines and lengths.

The toughest batsmen you have bowled to

Boult: In one-day cricket, you know the ball is not going to swing for long. Good batsmen know that if they get through those first 12 to 15 balls, then they have 47 overs of pretty good batting conditions. When you play against the likes of Rohit Sharma and Virat Kohli in the one-day game, you've got to be on the mark first ball, and you've got to give them nothing. You've got to realise you want to get them early, or else they are going to cash in and get big runs. That's always the challenge.

Southee: There's a number of batsmen who are difficult to bowl to but we [in New Zealand] are fortunate to bowl at some world-class players, day in day out. We are challenged in the nets regularly by quality batsmen like Kane [Williamson], Ross [Taylor] and the likes of Henry Nicholls and Tom Latham as well.

Our batsmen are challenged by our bowlers as well. You look at Kohli, [Steven] Smith, [Joe] Root and Kane, who are probably little bit ahead of the other guys.

Southee: "I guess you get a little bit smarter the older you get. But with extra pace, around mid-to-late 130s, you become more dangerous" © Getty Images

Boult: Playing Smith in Australia, on good wickets, where the ball doesn't swing, and where there are fast outfields - you can get tied into bowling where he wants you to bowl. He's very unique in the way he hits certain balls in certain areas. For example, if you're bowling at the top of off stump, he can hit that through square leg, or he can dab that through backward point. For the majority of batsmen in the world, that's a good ball. There are a few changes you need to make against him in terms of line and length. It's hard enough bowling in Australia as it is.

In England, the ball swings around nicely, but Joe Root has got a lot of runs there. I've always enjoyed bowling there, though.

Then you flip it and play Virat in Kanpur or Kolkata or something like that, where it's 40 degrees, you're hungry and you're sweating, and he's on 220 - that can be a totally different challenge.

The similar thing between them is that they are trying to come at you to try and put you off your natural length. If you can refuse to give into that and try and stack as many good balls on them as possible… everyone's human and they all make errors. Secondly, you're trying to back up your mate at the other end, and as a group you're trying to give them as little as possible and really put some pressure on them.

I've known Kane since we were little, so I've bowled to him quite a lot, to be honest. I suppose it's a similar plan. He's trying to get bowlers off their lengths and trying to get bad balls out of them. He's a very patient lad and has a brilliant technique. He can definitely hang in there. I don't know if I've got him out in the nets in a while. You've got to be quick to get him out in the nets. First couple of balls you might get him, but he's pretty switched on.

Andrew Fidel Fernando is ESPNcricinfo's Sri Lanka correspondent and Mohammad Isam is our Bangladesh correspondent

© ESPN Sports Media Ltd.