Exactly how does the weapon triangle works?

[Armchair General]

So I've been playing since Awakening and I never really had a reason to care until I got Fates. But even then, I'm not seeing much of a difference.

[Shadow Mir]

Mechanics wise, the weapon triangle gives bonuses to the winning side and penalties to the losing side. Shadow Dragon and the games afterwards made the effects dependent on the rank of the advantaged side, in addition to stripping the losing side of their weapon rank bonus.

Edited May 7, 2019 by Shadow Mir

[Ertrick36]

In Awakening, it depends on weapon ranks.

These are the bonuses/penalties each side gets:

Weapon Rank (advantageous side)	Weapon triangle advantage	Weapon triangle disadvantage
E or D	Hit rate +5	Hit rate -5
C	Hit rate +10	Hit rate -10
B	Hit rate +10, Attack +1	Hit rate -10, Attack -1
A	Hit rate +15, Attack +1	Hit rate -15, Attack -1

Eg. if Chrom has a B rank in Swords and faces a Barbarian with an E rank in axes, Chrom will receive a Hit rate +10, Attack +1 bonus, while the Barbarian will receive a Hit rate -10, Attack -1 penalty.

For the most part, it's kind of important at the start, but then eventually its value wanes because unit stats make much more significant an impact.  A unit with 50 speed and 40 luck is going to have an avoid stat of 95 - even more if they have certain skills and are paired up with an ally (there's no reason not to do this, ever).  So overall, the +/- 15 doesn't mean too much to them.

[Kempfnna]

In addition to the above the bonus may also vary slightly by game, but usually not by much

[Interdimensional Observer]

3 hours ago, Ertrick36 said:

These are the bonuses/penalties each side gets:

You forgot that WTD also neutralize a unit's Weapon Rank bonuses in the games where they are present. So for Awakening:

Type	C Rank bonus	B Rank bonus	A Rank bonus
Sword	Attack +1	Attack +2	Attack +3
Lance	Attack +1	Attack +1, Hit rate +5	Attack +2, Hit rate +5
Axe	Hit rate +5	Hit rate +10	Attack +1, Hit rate +10

So WTD for an A Sword unit is actually -3 Atk and whatever WTD deductions are inflicted by the enemy's weapon rank.

 

For pre-Awakening games:

Genealogy: +/- 20 Hit. 

Thracia 776: +/- 5 Hit.

Binding Blade: +/- 10 Hit, +/- 1 Mt.

Blazing Blade and Sacred Stones: +/- 15 Hit, +/- 1 Mt. Bonuses are doubled when using a -reaver weapon (except when two reavers go against each other) which also reverses the Weapon Triangle. These games also have a +5 Hit & Critical Bonus for hitting S in a Weapon Rank, but it is unaffected by the Weapon Triangle.

Path of Radiance and Radiant Dawn: +/- 10 Hit, +/- 1 Mt. So same as Binding Blade. Hard Mode RD removes the Weapon Triangle.

Shadow Dragon and Heroes of Light and Shadow: 

• Weapon triangle bonus:
  • +1Mt  if weapon is good against enemy’s weapon (weapon rank is A)
  • -1 Mt if weapon is bad against enemy’s weapon (enemy’s weapon rank is A)
• Weapon triangle bonus:
  • +5 if weapon is good against enemy’s weapon (weapon rank is E or D)
  • +10 if weapon is good against enemy’s weapon (weapon rank is C, B or A)
  • -5 if weapon is bad against enemy’s weapon (enemy’s weapon rank is E or D)
  • -10 if weapon is bad against enemy’s weapon (enemy’s weapon rank is C, B or A)
• Weapon Rank Bonus negated with WTD:

• Type	C Rank bonus	B Rank bonus	A Rank bonus
  Sword	Attack +1	Attack +2	Attack +3
  Lance	Attack +1	Attack +1, Accuracy +5	Attack +2, Accuracy +5
  Axe	Accuracy +5	Accuracy +10	Accuracy +15

 

Not that Mt (Might) is not the same as Atk. In any pre-Awakening game, having WTD weakens weapons with an effective bonus by 3 Atk, having WTA is an extra 3 Atk for effective weapons. So Marth's 5 Mt Rapier has only 12 Mt against Lance-using Cavaliers (and Knights), while Caeda's Wing Spear is 27 Mt against Sword-using Cavaliers. Awakening and Fates changed this to make the Weapon Triangle only affect Atk, not Mt. So Chrom's Rapier, the same 5 Mt as Marth's is 15 Mt against Lance-using Cavaliers.