GURPS melee treatise vol. 2: melee attack options

[elglin]

I will start with a side note that active defenses are extremely important in GURPS. On a more philosophical side, most folks going to war were much more concerned with getting out of it more or less alive - killing the opponent(s) was just a pretty efficient means to accomplish that. GURPS does model that appropriately.
Let me illustrate. A lowly grunt with perfectly average attributes, one point in Shield and a large shield - literally the minimum prerequisites to stand in a shield wall - has a Block of 3 + (10/2) + 2 = 10. That's right, he's got a 50% chance of blocking any attack.
A side note to a side note is that the probability difference between rolling 8 or under and 12 or under is 48%. That's right, 48% of the rolls land in the 9-12 range (inclusive). This means that increasing something of yours within this zone is almost always a good thing, and decreasing something through this zone is almost always a bad thing.

Now on to the meat. Most attack options (Basic Set + Martial Arts) let you choose a point in a two-dimensional space. One axis is balancing your own attack and defense, the other is balancing your attack against your opponent's defense.

Option	Own attack	Own defense
All-Out Attack (Determined)	+4	None
Committed Attack	+2	-2
Attack	0	0
Defensive Attack	0	+1
All-Out Defense	None	+2

There are two obligatory remarks. Committed Attack allows you an additional step which can come in handy tactically. Defensive Attack loses you 2 damage.

What to make of it? All-Out Attack is almost always pretty imprudent - that grunt above was having a 50% chance of blocking an attack, yours is likely better, and you are throwing it to the winds - unless you are pretty sure you don't get attacked (e.g. you are in the 2nd rank of a formation).
All-Out Defense doesn't get you any closer to the end of combat - tactically, however, it's a decent option after getting hit, when almost everything else is at pretty high penalties.
Committed Attack and Defensive attack are interesting options to fine-tune your Active Defenses in case when you have a bonus or malus to those (e.g. when you or the opponent has high ground).

Option	Own attack	Opponent's defense
Telegraphic Attack	+4	+2
Attack	0	0
Deceptive Attack	-2k	-k

The "k" in Deceptive attack can normally be anywhere between 1 and 5 inclusive - practically you're unlikely to use more than 3. Unless your character is the local equivalent of Miyamoto Musashi, that is.

Telegraphic Attack is mostly giving your opponent more than you yourself get - unless your opponent doesn't get an active defense (attack from the back, surprise, not otherwise defending) or has it so low that you actually get more of this (stunned, prone or otherwise very disadvantaged). In those select cases it actually makes a lot of sense - mostly to offset the penalty of a targeted attack.
Example: Joe the woodcutter got volunteered as the executioner by the local sheriff. Despite Joe having only a basic grasp of the big axe (effective Axe-9), he uses both All-Out Attack (he isn't getting retaliated by the guy on the chopping block) and Telegraphic Attack (the guy, if he isn't a Jomsviking, doesn't have an active defense), so he's striking at the neck at a respectable Skill-12, meaning he's got a 74% chance of actually hitting - not too bad for an unprofessional executioner.

Deceptive Attack is mostly a tool to fine-tune your effective attack. Say, you are attacking at Attack-16 against Block-10. You are at 49% to hit past the active defense. With one level of Deceptive Attack, you are at Attack-14 against Block-9, for approx. 56% hit chance. With two - you are Attack-12 against Block-8 for the same 56%. As a rule of a thumb, it almost always makes sense to Deceptive down to Attack-14 or 13, and sometimes down to 12 as well.

A final note is that these two axes are orthogonal. You can take a Defensive Telegraphic or a Committed Deceptive attack. Most of the time, your position along one of the axes will be chosen out of tactical considerations with the position on the other being complementary. Sometimes though, and this sometimes may get to "always" when you get to higher skill levels is that you fine-tune your active defense and then your attack. Say, with Attack-14 and Block/Parry-14, it can make sense to make a Committed Deceptive attack to the arm or leg, leaving you at an effective Attack-12 and Block/Parry-12 while putting a -1 penalty on the opponent's active defense.