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.

General overview

Defense is part of the game's learning curve. Typically, beginners may not be aware of defense, as guides often focus on general hand development and memorization of yaku. In the early stages of learning, a player may prioritize winning, since winning gives points. This is to some extent true, since you'll need to win at least one hand to finish first. However, it it not necessary to win every single hand to win a game.

Eventually, players learn the importance of minimizing deal-ins. Much less points are lost via tsumo or tenpai settlements than with deal-ins. In many instances, the points you lose matter more towards placement than the points you've gained. Still, a player has to produce hands, but they should know when to attack and when to defend.

Safe tiles

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

Defense focuses on finding anpai 「安牌」, or safe tiles. These are discarded tiles that opponents cannot win off of. 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.

Japanese mahjong offers players the ability to determine, deduce, and infer safe tiles. Players may show threats you may want to defend against, such as riichi declarations or particularly valuable open hands.

Sakigiri

Main article: Sakigiri

Sakigiri is the act of discarding tiles before they become dangerous. When sakigiri is mentioned, it usually comes at the cost of tile efficiency (hand speed).

Players will often receive at least one tile that another player could've won with. Sometimes, you can get those "winning" tiles before an opponent reaches tenpai. By discarding those tiles before opponent tenpai, it won't be dangerous. This technique is best done when you don't care about winning (e.g. you have a cheap hand). You could also use the tile in your hand, or fold by never dealing said tiles.

Note: if a dangerous tile does nothing in your hand and cannot be used to improve hand waits, then you should discard that tile early, no matter which tile you have.

Techniques to find safe tiles

A number of techniques can be used to determine safe tiles. All of them utilize visible tiles from the discards, dora indicator, 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.

Suji

Main article: Suji

Suji focuses on taking advantage of the furiten rule and the most common type of wait.

A ryanmen wait, a two-sided wait to complete a sequence (e.g. {23} waiting for 1 or 4), is the most common wait in the game, appearing in ~50% of all hands. A ryanmen always waits on tiles that are 3 numbers apart, such as 1-4 or 4-7.

Therefore, when a tile is safe, the other tiles that are 3 apart become safer. For instance, if a player has discarded 4-pin, the 1-pin and 7-pin become safer against that player. Neither 1 or 7 is perfectly safe, however. These intervals of 3 are called "suji intervals".

It is important to note that the middle tiles (4, 5, 6) require two tiles to be considered true suji. 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 open wait. The 4 is only full suji if both 1 and 7 are safe.

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 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. But if the hand reaches tenpai with a ryankan intact, then it must discard one of the tiles. In this case, 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 most 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.

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.

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