Answers.Body: <p>They're <em><strong>connected</strong> knights</em>.</p>
  
  <p>As the other answers said, this isn't typically that smart a thing for knights. OTOH, <em>rooks</em> are very often made stronger by connecting them (it allows them to thwart any queen intrusion). Thus you'll more often hear about it being “a <a href="https://chess.stackexchange.com/a/476/15238">good idea to connect rooks</a> now”. But I think I've also heard the term used with knights. Just, knights tend to serve more of a tactical role than solid defense of the back-rank, and they're usually better protected by pawns or bishops, as these don't reduce their mobility in the way mutual knight defense does.</p>
  
  <p>For pawns, the term <em>connected</em> of course means something different, since two pawns can never protect each other mutually.</p>
  
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Answers.Body: <p>I've seen the term &quot;redundant knights&quot;. In general, redundant pieces are pieces can get in each other's way. Here's a quote I could find about the general principle, but not specifically about knights:</p>
  <blockquote>
  <p>Interestingly, two of Lasker’s other points were:</p>
  <p>• The principle of
  redundancy: Two pieces that move the same way on the same squares can
  easily get in each other’s way, while two pieces that never get in
  each other’s way – like two bishops – are better coordinated. This was
  verified by computer analysis by Larry Kaufman 60 years later! Larry’s
  important contributions are noted in several places in this book.</p>
  </blockquote>
  <p>Heisman, Dan. Elements of Positional Evaluation (Kindle Locations 1035-1039). SCB Distributors. Kindle Edition.</p>
  <p>Googling specifically for &quot;redundant knights&quot; I found this (also by Dan Heisman):</p>
  <blockquote>
  <p>For example, he calls two knights that guard each other “redundant knights” and notes that this is usually a weak setup.</p>
  </blockquote>
  <p><a href="https://chesscafe.com/coordination/" rel="noreferrer">https://chesscafe.com/coordination/</a></p>
  <p>I don't have access to that article as I'm not a chesscafe.com member so I don't even know who &quot;he&quot; is (maybe Lasker or Kaufman?), so if anyone with full access to that article can provide more context, I'll happily edit my answer.</p>
  
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Answers.Body: <p>As far as I know, there's no standard terminology for this. It is usually not the best configuration for two knights; they are stronger when positioned side by side, so that they cover a lot of squares in the same area.
  If I had to describe the situation, I'd go for something like 'mutually protecting knights'.</p>
  
  <p>There's a related concept which is called the 'superfluous piece' or <a href="https://www.chess.com/article/view/an-quotextraquot-piece" rel="noreferrer">'extra piece'</a>, which most often happens with two knights. One of them occupies an outpost, and the other one is basically doing nothing but waiting to recapture on or move to that square when the first one is exchanged.</p>
  
  <p><a href="https://i.sstatic.net/3U9sH.png" rel="noreferrer"><img src="https://i.sstatic.net/3U9sHm.png" width="300" /></a></p>
  
  <p>Here, Black's next move was 11... Ne8, to make the c3 knight superfluous.</p>
  
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Answers.Text: Black is faced with two threats, Nxf6 doubling the pawns and Nxc7. Black has two choices: 11...Nxd5 and 11...Ne8, the later is better because it makes the c3 knight redundant.
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Body: <p>How to describe two knights defending each other?</p>
  
  <p>Linked knights? </p>
  
  <p>Doubled knights?</p>
  
  <hr>
  
  <p>In Chinese Chess, two 马 (horse/knight)s protecting one another is quite common, and there is a standard terminology: "连环马".</p>
  
  <hr>
  
  <p>There is a real case: "German Chess Prodigy Surprises Boris Gelfand With A Brutal Queen Sacrifice"(<a href="https://www.youtube.com/watch?v=l37hlb32Rs0" rel="noreferrer">https://www.youtube.com/watch?v=l37hlb32Rs0</a>)</p>
  
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2018-10-22T00:30:37.073Z
Comments.Text: @BenCrowell It's weak in chess simply because one of the knights hinders the others' movement. As for Chinese chess, I'm only a casual player, but I would imagine it is because not many pieces are able to protect each other in Chinese chess.
Comments.UserDisplayName: Quintec
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2018-10-22T03:35:45.840Z
Comments.Text: @Quintec No, in Chinese Chess, every kind of pieces can protect each other.
Comments.UserDisplayName: Zhang Jian
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2018-10-22T03:41:58.147Z
Comments.Text: @Quintec except the general/king, of course.
Comments.UserDisplayName: Zhang Jian
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2018-10-22T08:39:11.140Z
Comments.Text: They are simply _covering_ each other. And, as always, when pieces cover each other they restrict the movement of each other,, but only by 1 field. Not a bad thing, usually.
Comments.UserDisplayName: TaW
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2018-10-22T09:36:50.420Z
Comments.Text: @BenCrowell, I think it's two reasons. 1 rook value. In western chess 2N is better than 1R, while in ch chess, 1R is generally thought to be better than 2N. 2 pawns. In ch chess, connected Ns are much less likely to be broken by pawns.
Comments.UserDisplayName: jf328
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2018-10-22T13:40:08.837Z
Comments.Text: @ZhangJian Yes, but from starting position it is hard to get two pieces to protect each other. 炮 it requires an awkward formation, 车 are extremely separated at the start, and the defensive pieces protect each other, but 马 are extremely versatile. Then again, this is just a guess.
Comments.UserDisplayName: Quintec
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2018-10-22T21:21:13.060Z
Comments.Text: @jf328 Interesting... when I first learned chess way back when, I was taught that knights and bishops were each worth exactly 1/2 of a rook, or 2.5... but a quick search yields no results that I can find where a knight or a bishop is worth less than 3.
Comments.UserDisplayName: Michael
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2018-10-24T07:23:38.627Z
Comments.Text: @Quintec In Chinese Chess, 车s 马s and 炮s protecting each other are all common, and have special terminologies for them (霸王车 连环马 担子炮). At the beginning, you can (and even should) form the connection. For example, developing 马 or 相/象 at the first move.
Comments.UserDisplayName: Zhang Jian
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2018-10-24T11:50:33.627Z
Comments.Text: @michael That is not very accurate - in most situations I would prefer two bishops/knights or one of each over a rook
Comments.UserDisplayName: Quintec
Tags: <knights><terminology>
Title: How to describe two knights defending each other?
ThreadText: # How to describe two knights defending each other?
  
  (Asked by: username_0 on 2018-10-21)
  
  How to describe two knights defending each other?
  
  Linked knights?
  
  Doubled knights?
  
  ---
  
  In Chinese Chess, two 马 (horse/knight)s protecting one another is quite common, and there is a standard terminology: "连环马".
  
  ---
  
  There is a real case: "German Chess Prodigy Surprises Boris Gelfand With A Brutal Queen Sacrifice"(<https://www.youtube.com/watch?v=l37hlb32Rs0>)
  
  **Tags:** knights, terminology
  
  > **Comments:**
  > **username_1**: @BenCrowell It's weak in chess simply because one of the knights hinders the others' movement. As for Chinese chess, I'm only a casual player, but I would imagine it is because not many pieces are able to protect each other in Chinese chess.  
  > **username_0**: @username_1 No, in Chinese Chess, every kind of pieces can protect each other.  
  > **username_0**: @username_1 except the general/king, of course.  
  > **username_2**: They are simply _covering_ each other. And, as always, when pieces cover each other they restrict the movement of each other,, but only by 1 field. Not a bad thing, usually.  
  > **username_3**: @BenCrowell, I think it's two reasons. 1 rook value. In western chess 2N is better than 1R, while in ch chess, 1R is generally thought to be better than 2N. 2 pawns. In ch chess, connected Ns are much less likely to be broken by pawns.  
  > **username_1**: @username_0 Yes, but from starting position it is hard to get two pieces to protect each other. 炮 it requires an awkward formation, 车 are extremely separated at the start, and the defensive pieces protect each other, but 马 are extremely versatile. Then again, this is just a guess.  
  > **username_4**: @username_3 Interesting... when I first learned chess way back when, I was taught that knights and bishops were each worth exactly 1/2 of a rook, or 2.5... but a quick search yields no results that I can find where a knight or a bishop is worth less than 3.  
  > **username_0**: @username_1 In Chinese Chess, 车s 马s and 炮s protecting each other are all common, and have special terminologies for them (霸王车 连环马 担子炮). At the beginning, you can (and even should) form the connection. For example, developing 马 or 相/象 at the first move.  
  > **username_1**: @username_4 That is not very accurate - in most situations I would prefer two bishops/knights or one of each over a rook  
  
  ---
  
  ## 3 answers
  
  ### Answer by username_5 on 2018-10-21. Score: 27
  
  They're ***connected** knights*.
  
  As the other answers said, this isn't typically that smart a thing for knights. OTOH, *rooks* are very often made stronger by connecting them (it allows them to thwart any queen intrusion). Thus you'll more often hear about it being “a [good idea to connect rooks](https://chess.stackexchange.com/a/476/15238) now”. But I think I've also heard the term used with knights. Just, knights tend to serve more of a tactical role than solid defense of the back-rank, and they're usually better protected by pawns or bishops, as these don't reduce their mobility in the way mutual knight defense does.
  
  For pawns, the term *connected* of course means something different, since two pawns can never protect each other mutually.
  
  
  ---
  
  ### Answer by username_6 on 2018-10-21. Score: 15
  
  I've seen the term "redundant knights". In general, redundant pieces are pieces can get in each other's way. Here's a quote I could find about the general principle, but not specifically about knights:
  
  > Interestingly, two of Lasker’s other points were:
  >
  > • The principle of
  > redundancy: Two pieces that move the same way on the same squares can
  > easily get in each other’s way, while two pieces that never get in
  > each other’s way – like two bishops – are better coordinated. This was
  > verified by computer analysis by Larry Kaufman 60 years later! Larry’s
  > important contributions are noted in several places in this book.
  
  Heisman, Dan. Elements of Positional Evaluation (Kindle Locations 1035-1039). SCB Distributors. Kindle Edition.
  
  Googling specifically for "redundant knights" I found this (also by Dan Heisman):
  
  > For example, he calls two knights that guard each other “redundant knights” and notes that this is usually a weak setup.
  
  <https://chesscafe.com/coordination/>
  
  I don't have access to that article as I'm not a chesscafe.com member so I don't even know who "he" is (maybe Lasker or Kaufman?), so if anyone with full access to that article can provide more context, I'll happily edit my answer.
  
  
  ---
  
  ### Answer by username_7 on 2018-10-21. Score: 10
  
  As far as I know, there's no standard terminology for this. It is usually not the best configuration for two knights; they are stronger when positioned side by side, so that they cover a lot of squares in the same area.
  If I had to describe the situation, I'd go for something like 'mutually protecting knights'.
  
  There's a related concept which is called the 'superfluous piece' or ['extra piece'](https://www.chess.com/article/view/an-quotextraquot-piece), which most often happens with two knights. One of them occupies an outpost, and the other one is basically doing nothing but waiting to recapture on or move to that square when the first one is exchanged.
  
  [![](https://i.sstatic.net/3U9sHm.png)](https://i.sstatic.net/3U9sH.png)
  
  Here, Black's next move was 11... Ne8, to make the c3 knight superfluous.
  
  > **Comments:**
  > **username_8**: Black is faced with two threats, Nxf6 doubling the pawns and Nxc7. Black has two choices: 11...Nxd5 and 11...Ne8, the later is better because it makes the c3 knight redundant.  
  
  ---
  
  