Defense

Defense in Japanese mahjong means to avoid dealing into other players' hands by not discarding winning tiles. Defense is an important skill, especially when other players call riichi and/or have a high scoring hand. All else equal, a player with a lower "deal-in rate" will have a higher chance of winning the game.

Overview

Choosing the proper discard (or the wrong one) may determine the result of many games.

Defense focuses on finding safe tiles, or tiles that other players cannot win with. Players use defense against a dangerous threat, such as a riichi declaration or a valuable open hand.

Newer players may not be aware of defense, since guides often focus on general hand development and memorization of yaku. Beginners may prioritize winning every hand, since winning gives points. However, winning every single time is infeasible. Defense is useful whenever a win is too far away, too risky, or otherwise impossible. It focuses on minimizing deal-ins: tsumo payments and tenpai settlements result in a much smaller loss than a deal-in. In many cases, the points you lose matter more than the points you gain. Overall, while winning hands is still important, players should know whether to attack or defend.

When defending, players should take into account all visible tiles, including tiles in discard piles, the dora indicators, tiles in your own hand, and any called tiles.

Techniques to find safe tiles

A number of techniques can be used to determine safe tiles. All of them rely on "visible tiles", which include tiles from the discard pile, the dora indicators, opponents' tile calls, and the player's own hand.

Furiten and genbutsu

Main articles: Furiten and Genbutsu

The most important defense technique. Genbutsu involves tiles that are 100% safe against a player, due to the furiten rule:

• Any tile that an opponent discarded is 100% against them.
• After an opponent declares riichi, any tile anyone discards (and not won off of) is 100% safe against that riichi player.
• Any tile that the player to your left has discarded this turn is 100% safe for this turn only.

Honors

Honor tiles with multiple copies visible are generally safer. This is because the honor tiles cannot form sequences, meaning they are harder to wait off of.

• Honor tiles you can see all four copies of are safe against everything except kokushi musou. If kokushi isn't possible (e.g. all four copies of a different honor/terminal are also visible), then these honors are 100% safe.
• Honor tiles you can see three copies of are extremely safe. They can only be won off a tanki wait or kokushi musou. Even yakuhai are safe.
• Honor tiles you can see one or two of are relatively safe. They become safer if at least one copy has been discarded by any player. Guest winds are safer than yakuhai.

"Live" (unplayed) yakuhai can be dangerous, becoming more dangerous as the game goes on. They are particularly dangerous against a suspected honitsu hand. They can also be dangerous for an open hand without any apparent yaku.

Suji

Main article: Suji

Suji takes advantage of the furiten rule and uses it to eliminate the most common type of wait.

Theory

Suji states that, when a number tile is safe against a player, other tiles that are 3-apart become safer. A "safe" tile is a tile that would trigger furiten (either a tile discarded by that player, or any discarded tile after that player calls riichi).

This is because a ryanmen wait, a two-sided wait to complete a sequence (e.g. {23} waiting for 1 or 4), is the most frequent wait in the game. A ryanmen always waits on tiles in an interval of 3, such as 1-4 or 4-7. If a player discards 4-pin, then that player cannot have a ryanmen wait on 1-pin or 7-pin without being in furiten. Therefore, when 4-pin is safe, 1-pin and 7-pin become safer. While neither 1-pin or 7-pin are perfectly safe, they are significantly safer than normal.

It is important to note that the middle tiles (4, 5, 6) require two tiles to be considered true suji. This is because the 4 is part of two suji intervals: 1-4 and 4-7. If a 1 is discarded, a player could still have a 4-7 ryanmen. The 4 is only full suji if both 1 and 7 are safe.

There are three major intervals: 1-4-7, 2-5-8, and 3-6-9. These intervals of 3 are called "suji intervals".

Safety Level

Some suji are safer than others:

• Suji terminals (1 and 9) are the safest, as they can only be targeted by a tanki or shanpon.
• Suji 2 and 8 are the next safest. They can be targeted by a tanki, shanpon, or kanchan.
• Suji 3 and 7 are the most dangerous, though still reasonably safe. They can be targeted by a tanki, shanpon, kanchan, or penchan.
• "Full" suji 4, 5, and 6 are about as safe as suji 2 and 8. "Half" suji 4, 5, and 6 are as safe as a non-suji 2 (not safe).
  • Note: Full suji is when both suji interval tiles are safe. Half suji is when only one suji interval tile is safe. So a 1 being safe makes 4 half suji; both 1 and 7 being safe makes 4 full suji.

Using suji on the riichi declaration tile is more dangerous than normal. This is because of the ryankan shape (e.g. 135, 246, or 357). Ryankans are often kept as they can improve tile efficiency. If the hand reaches tenpai with a ryankan intact, then one of its tiles must be discarded. This creates a suji trap. For example, with a ryankan of 135, a player can discard the 5 and wait on the suji tile 2.

In addition, opponents may intentionally take advantage of this strategy by setting up suji traps, like discarding a 6 and waiting on the 9. Players may also declare riichi on a one-sided wait or a shanpon wait, where suji would be useless. Relying only in suji to defend will result in many play-ins. Therefore, suji should be used when genbutsu tiles have ran out, or in Uchi-mawashi.

Kabe

Main article: Kabe

Kabe is a tactic similar to suji. If all four copies of a tile are visible, then it is impossible to have certain types of sequence wait on certain tiles nearby.

For example, if you can see all four copies of 3-pin, then 1-pin and 2-pin cannot possibly be part of a sequence wait. This is because no opponent can possibly have a 23 or 34 shape, because no opponent can have a 3 in the first place.

Only tiles outside the blocked-off tile (i.e. tiles further from 5) are safe. Tiles towards the middle of the "blockade", such as 4-pin or 5-pin when all four 3-pin are visible, are not much safer, similar to how half suji are not much safer.

Like suji, other waits - specifically, waits that are not sequences - are still possible. It is also possible to target 3 or 7 with a penchan. Overall, kabe is comparable to suji (though kabe is safer), and should be used in a similar fashion.

When to defend

The "push/fold" decision - i.e. when to go for a win vs when to defend - is one of the many critical decisions a player can make. A concrete answer is difficult, so here are factors to consider:

• Hand progress: At 2-shanten or higher, it is usually worth folding if able - tenpai is too far away. 1-shanten with poor acceptance is a similar story.
  • Tile acceptance / waits at tenpai: It's much better to attack if you have good waits (wait with >= 6 tiles remaining). Similarly, at 1-shanten, it's best to have strong tile acceptance.
• Hand value: Cheaper hands are not worth pushing as much.
• Situational analysis: Especially when close to all last, consider what happens if you win, if you deal in, and if an opponent tsumos. For example: if it's all last, 4th place declares riichi, and you are 3rd with only a 1000 point lead, you dealing in and having opponent tsumo would both result in you ending in 4th. Therefore, you would be forced to attack.
• Number of safe tiles in hand: If you have no reasonably safe tiles to discard, you may have no option but to attack. You can fold later if safe tiles are revealed.
• Turn count (Number of safe tile types available): As more tile types become safe, the more dangerous the other tiles become (see Suji counting for more detials). Therefore, as the game progresses, you should be more willing to fold. The longer the game goes on, the more safe tiles are revealed, and thus the more dangerous it is to push.

Sakigiri

Main article: Sakigiri

Sakigiri is the act of discarding tiles before they become dangerous.

In general, tiles are safer when discarded earlier; if an opponent isn't in tenpai yet, they can't win. Sakigiri means discarding a potentially-dangerous tile early, even if it would come at the cost of hand speed. This technique is best used when you don't care about winning (e.g. you have a cheap + slow hand, or you have a large lead). You could also use the tile as part of a tile group, or fold by never dealing said tiles.

Usually, when sakigiri is mentioned, it comes at the cost of hand speed. This isn't always the case, though. If a dangerous tile would do nothing in your hand, and can't be used to improve your hand waits, discard that tile early.

The ways of defense and offense

Betaori

Main article: Betaori

Betaori ("folding") is pure defense - it focuses on discarding nothing but safe tiles. In this state, a player has completely abandoned all hope of developing a winning hand, only trying to minimize the chance of dealing in. At times, it may be needed to break tenpai for defense. The essence of betaori is to always discard the safest tile first. Even suji and hell-wait honor tiles should not be discarded before genbutsu.

Kanzen shinko

Kanzen shinko ("pushing") is the way of complete offense. A player basically ignores the opposing tenpai and proceeds to attack normally. It can be used with a very strong hand, a situation where a win is required, or in any case where the hand contains very few safe tiles. In the last case, one can switch to betaori if tiles in the hand become safe.

Mawashi uchi

Mawashi uchi is a half-way style. A player will aim to discard relatively safe tiles while still aiming for tenpai. Discardable tiles include honors, suji tiles and no-chance kabe tiles. From this state a player may fall back to betaori upon drawing dangerous tiles, or attack when reaching tenpai. This style is not recommended for beginners due to requiring strong push/fold judgement (it is easy to discard recklessly, claiming it's "mawashi"). It is most appropriate to use when in a good shape iishanten for a strong hand.

External links

• Osamuko.com

Basic Defense Techniques in Mahjong

• Betaori and Suji

UmaiKeiki’s defense guide — Betaori and Suji