What you're running into is a problem with tactics, not the rules. If there are two characters that are near eachother, but not adjacent, then you are correct that if the faster combatant moves in close, they will be attacked first. However, they don't have to take the Move or Move and Attack action to get the first strike.
Instead, take the Wait action. Wait allows you to:
Do nothing unless a particular
event you specified in advance
occurs before your next turn; e.g., a
foe moves into range. If that happens,
you may transform your Wait
into an Attack, Feint, All-Out Attack
(you must specify the option before
acting), or Ready maneuver. If you
are reacting to someone else, this
interrupts his turn, but he can
resume it after you’ve acted.
Emphasis mine. In this case, the faster character should Wait until their enemy comes in melee range, and then Attack or All-Out Attack. Alternately, you could take the All-Out Attack action directly. That lets you move up to half your speed as part of the attack. Note, however, that the character that chooses to move up might choose to take an All-Out Defense (Dodge) which lets them move half their speed and get a +2 to their Dodge defense, possibly negating the stationary character's attack. GURPS melee combat between two intelligent opponents is a lot like actual combat between intelligent opponents; it's a string of bluffs and double-bluffs to try and trick your opponent into giving you the advantage.
In every system that I know of that includes tactical combat, there is a way to respond to an enemy's action like this.
Another possible option is an initiative system from one of the World of Darkness systems. Basically, you have every combatant choose their actions in reverse initiative order: the slowest character picks their action, then the next slowest, all the way to the highest. Once all actions are selected, you execute in order of initiative. Using your situation as an example:
- Slow fighter declares intent to stay put, and defend.
- Fast fighter declares intent to move up to slow fighter.
- Fast fighter moves up.
- Slow fighter starts defending.
Then, the next round, you do it again. I'm pretty sure this system also had you re-roll initiative each round, so different people went at different times each round.
In combats that involve more than two characters in GURPS, you can use your opponent's reluctance to make the first move to your advantage. Since facing matters in GURPS, you can use the time your opponent spends not charging you to set up a flanking position with an ally, or move off to deal with another threat, or just hold your opponent still until your ranged attacking allies can whittle them down.
The reason for this is that GURPS is meant to model reality very closely, and with a 1 second combat round, there just isn't time to move several yards and also make an accurate attack without also giving up your defenses. If you watch actual melee combat, when the fighters get close they typically have a strongly defensive stance until one of the combatants makes an attack. This would be modeled by both combatants taking All-Out Defense actions until both were in melee range, and then starting to use other Attack options.
First, it's good if you can find out why the player is playing a non-magic user. You found out it matches his character, which is good, but it might be good to find out what type of gameplay he likes, so you know what to provide and what not to avoid, which might be tricky if you yourself always prefer to player magic-using characters.
Some reasons players might avoid magic-using PC's include:
They don't easily relate to magic powers, and are more interested in non-magic human experiences and situations.
They don't know how the magic system works, and don't want to have to figure out the complexities of it.
They are interested in some other aspect of play (say, detailed combat), and want to focus their skills on that so it will be more interesting and/or their character will be better at fighting.
It's good to know if the reasons are like the above in that there is disinterest in magic, because if so, it may not help to offer them, say, magic items, or a special kind of super power, or even unrealistic martial arts abilities, if they are similar to the things the players don't like about magic, that had them choose to be non-magic users.
In general, I think if a player chooses to be a non-magic fighter type, they will probably appreciate being given interesting combat situations where their character is valuable. Fortunately, you're playing GURPS, which is the best system I know for that. Use tactical combat with a map, and include foes the fencer will be useful against, and/or more (or more resistant) foes than the magic will be able to take care of.
There are other reasons players might choose non-magic-using PCs, which do invite adding magic or magic-like abilities:
A player might have a super-skilled fighter concept, and enjoy meeting a master trainer who can teach them super fighting skills, which may be somewhat magic-like. These can offer not just fighting skills, but skills such as extreme abilities in hiding, jumping, climbing, silent movement, chi powers, possibly magic resistance through will/meditation/chi, and so on. Probably the best source for this sort of thing in GURPS is GURPS Martial Arts.
A player may not want to cast spells, but might like having/using magic items. If there are enough of magic items available that are useful for non-casters, and the groups gives enough of them to the non-fighter PC, then that can give that PC abilities the others don't have.
There may be other types of super powers available in your world that are appropriate to the non-magic-user PC, such as religious-based powers, or psychic powers, or super powers, or whatever. If the player is interested, those can give the player abilities that the magic-users don't have.
In many games, there is so much common magic and magic-like abilities, and they are so useful and/or powerful, that PCs who avoid magic are just going to be much less powerful than those who do. Fortunately, GURPS isn't one of those unless the setting or magic system used makes magic very common and strong. Standard GURPS Magic is quite strong and if most or all of the spells are available and common, there is a lot they can do, but there are still good niches for good fighters.
Another approach can be to have the adversary NPCs notice if/when the players defeat their minions or some situation/puzzle with a conspicuous use of magic. The adversary NPCs may then try to use that knowledge against the party, and come up with ways to challenge the party that counter the magic they know the party has. Something that looks like it can be burned, but can't, to bait and use up the magic of the pyromancer, for example. This can create a situation where the party needs to fight, and the fighters get a chance to shine.
Similarly, you can study the non-magic-user PCs and see what abilities and knowledge they have that are outside the domains of the magic users, and let the PC get chances to notice those. In your case, the sailing thing comes to mind. If he's the only one with seamanship and they're on a ship, he'll have advantages in knowledge, getting around the ship, not getting seasick, and avoiding DX penalties for a rocking deck, etc.
Having studied the PC's abilities, especially when (as you wrote) the player is not as familiar with the game system as you are, you may want to give that player extra information and prompts and ideas throughout the game, based on those abilities, because there are things the PC might think of that the player may not, and this can help the player grow familiar with the opportunities their skills offer.
There may also be places or factions in your campaign setting, who are opposed to magic, or certain types of magic, so that it may be criminal or at least attract attention of ill will if people know you use that magic.
GURPS-specific tips:
Always use a hex map. This makes combats more interesting for fighters, and results in more situations where fighters are needed and useful, and casters have more difficulties, due to range, obstacles, being engaged by attackers, etc. When you're using all the rules, including range penalties and casting times, it often isn't actually all that superior to be a mage in GURPS, as it may take too long to cast a spell, or the target may be too far away, or there may be obstacles to line of sight, or someone may come grapple you, etc.
Get GURPS Swashbucklers for some realistic & cinematic fencing-related abilities, tricks and equipment, as well as some sailing-related stuff.
Have situations where the characters have several challenges with not a whole lot of time to rest in between. In GURPS Magic, the magic-users use up mana when they cast spells, and so they'll need to use it sparingly, or run out of mana by the time they get to the later situations. Meanwhile, the fighters tend to be able to do more per fatigue point. The party may even realize that it needs to save mana for healing and even to restore fatigue on the fighters, if it is to overcome a series of challenges without running out of mana to cast spells.
There are situations in GURPS that call for fencers, such as multiple attackers, or dangerous foes who attack multiple times per turn and are best parried, or that are best disarmed.
GURPS has the concept of Low Mana and No Mana zones, and Aspected Mana Zones and so on, which can also take the magic users down a notch in some places.
Best Answer
I been playing GURPS since 1987 and the basic combat of attack, defend, damage can indeed bog down for even moderately skilled players. In reality people have options to get around the defenses of a skilled opponent and for some added complexity GURPS can emulates these options.
First off the players should not pair off with their opponents but should at least double team opponents. In the two-on-two fight this means that one player can force a step back by an enemy then the second player can strike, forcing their opponent to use their base defense.
They could position themselves so one can limit the target's defense (page 390). A side attack get -2 to defense and a rear attack permits no defense roll.
The player can choose to beat down their opponents' shields by striking at their weapons and especially the shield (pages 484, 485).
A skilled player can chose to Feint, basically a contest of weapon skill, and if the player wins the contest the difference is applied as a negative to the opponent's defenses (page 365).
A limb strike to the arm or leg can be effective as there is often little armor in those locations (page 398).
A step and evaluate can be used to gain up to +3 to hit (page 364). While it extends combat in-game time, it takes little time to resolve in table time: the player just declares he is evaluating.
Finally, historical melee combat is as much a physical contest as it is about weapon play. Slams can be used to knock the opponent down to a prone position with all his weapons unready (page 371) and at a -3 to defense. Grappling can be used to immobilize an opponent for a friend.
Look at Knockback on page 278. Basically, for every multiple of ST-2 on damage before armor is subtracted, the opponent is knocked back a hex. More critically it forces them to make a DX, Acrobatics, or Judo roll or fall down.
Don't forget to apply the shock roll once anybody takes damage. For example 4 damage means the person is -4 to all rolls until the next round (page 419). Any damage over HP/2 will force the target to roll vs Health for stunning and knockdown (page 420).
The biggest issue the player will find when using these options isn't their complexity, but figuring out when they can be effectively used. For example, trying to slam a target with a lot more HP than you wouldn't be a good tactic.
Finally, remember the NPCs' morale. Rarely will an intelligent person fight to the death. Some will run away with a just a broken sword arm – and in a two person fight, that will likely cause the other person to run away as well.