MAGIC WEAPONS: The brief treatment of magic weapons given here in the combat section matches fairly well with the OD&D rules. We'll see if that's still the case when Holmes gets into more depth in the magical items section.
As for magical armour, Holmes is going for the simpler system introduced in Supplement I. In OD&D, the shield's magical bonus only comes into play one-third of the time. In Supplement I, this is changed so that the bonuses always work together. Holmes has gone with the latter, and in the interests of simplicity I'm happy.
COMBAT ROUNDS, TIME AND MOVEMENT IN MELEE: The big change here is that a combat round is now 10 seconds instead of 1 minute. I'm not sure why Holmes bothered, to be honest, but it does head off the inevitable questions about why characters only get one attack per minute from those who can't wrap their heads around the abstraction. The biggest change this makes is that now characters and monsters can't move as far per round as they could before. Otherwise it has very little effect mechanically, unless you want to take spell durations and the like into account.
The next few sentences are the one bit where Holmes loses me completely. Dagger-wielders here are given the ability to attack twice per round, while those wielding heavy weapons like two-handed swords can only attack every other round. And yet, every weapon deals 1d6 damage. There's a wonky rule if ever I've seen one, and it's been duly noted by every other blogger that's ever analysed Holmes. It's probably an attempt to duplicate a similar rule from the Man-to-Man combat rules in Chainmail, but those rules factored in weapon type vs. armour. This one doesn't, and so it's majorly flawed. I'd be inclined to house-rule it, but given the strictures of my campaign I have to include this ridiculous design.
So here's what I'm thinking. As I've mentioned earlier, the transition in my campaign from OD&D with supplements to Holmes Basic is being handled by a change of leadership within the Adventurers' Guild, and the back-to-basics ethos that came with it. But looking at the above rule, there's a certain type of character class that benefits here. One that primarily uses small weapons in melee. That is, of course, the Thief. So I'm thinking that maybe the new guild leadership is under the thumb of the Thieves' Guild, who are changing the regular training to benefit themselves. About the time the players hit 3rd level this manipulation could be exposed, and that's when the leadership gets overthrown and the AD&D rules start to filter in.
WHO GETS THE FIRST BLOW?: Basically, in Holmes D&D the guy with the highest Dexterity goes first in melee. Again, it's a big advantage to Thieves, isn't it? The system from Chainmail that factored in weapon lengths and speeds was much better than this rule, which I guess was extrapolated from a line in OD&D about Dexterity influencing initiative. There's also a problem in that you need a Dexterity score for everybody for this rule to work, but there are none provided in the monster descriptions. It's easy enough to roll on the spot, or just to assume that most monsters have a Dexterity of 10, but it's still an oversight.
THE PARRY: There were rules for parrying in Chainmail, but Holmes hasn't gone with those. His rules are simpler, just granting the defender a bonus to AC in exchange for forgoing his next attack. And if the attacker rolls exactly the number needed to hit, he breaks the defender's weapon.
MELEE RESOLUTION - CONQUER, WITHDRAW, SURRENDER OR DIE!: That's the best sub-heading in the book, without a doubt. But the section doesn't live up to the hype, simply providing some cursory rules for retreat and surrender.
COMBAT EXAMPLE: The first combat example details a simple exchange of blows between a big goblin and "Bruno the Battler". All it shows is how to do regular attack rolls and damage, but it does provide me with an NPC to have hanging around the Adventurers' Guild. Bruno is presumably a fighter, and we learn that he has a Dexterity of 13, wields a sword, and wears chain mail and a shield. He also has 6 hit points, which probably makes him first level.
SECOND COMBAT EXAMPLE: The second example has a whole adventuring party having a random encounter with six giant spiders. The adventuring party is made up of the aforementioned Bruno, Malchor the Magic-User (who has previously appeared in the book), Mogo the Mighty (presumably another Fighter), and Clarissa the Cleric, among unnamed others. The adventurers take out the spiders, but poor old Bruno is killed by a poisonous bite. Alas, I must scratch him from my list of active NPCs. His surviving comrades will talk about him should they meet the PCs, though.
As for them, we learn the following. Malchor can cast the Sleep spell. It looks like Bruno and Mogo were both armed with bows. Mogo has a Dexterity of 9, wields a sword, wears chainmail, and has but 3 hit points. Clarissa has a Dexterity of 6 and wields a mace.
It's interesting to note that in this example Holmes does suggest rolling Dexterity for monsters on the spot, so at least that little discrepancy is dealt with. But I'm still wondering, why did Mogo and the spider have two attacks each after Bruno's death? Or was it simply a short way to describe the passage of two rounds?
The comments at the end state that readied spells go off first, followed by missile fire, then melee. And that's as much as we get on initiative, folks.