The whole thing started because of a random encounter. While I knew was in the region I had no clue that in a Orc hunt was in the works until it occurred. Luckily it happened late in the session so I had some time to prepare. Otherwise I would have winged at least an orc outpost and then prepare something more elaborate later. A lot of my campaigns have moments like this and it is what I feel the essence of running a fantasy sandbox.
Another I will point is that I have no problem with high level parties going up against low level opposition. When you run sandbox campaigns that can and will happen. Of course there are always consequences even if they manage to spectacularly slaughter hundreds as they did in this adventure. And those consequences led to... yup even more adventures. Perhaps against a more experienced foe or perhaps not.
The map is actually something I drew up long ago
I been working on a master map of the Majestic Wilderlands for a while so I just exported what I had done and overlaid the information from this map on it.
I plan to use this at some point to use this as the basis for something I call a mega-wilderness.
Players been having a go at the Orcs of Deathwoods since my campaigns of the early 80s. Somehow the orcs always managed to bounce back.
The use of Battlesystem went well. As it turned out it was good that brought it as I had to use the counter for large rooms in the orc warrens with each counter representing four orcs.
Basically the way Battlesystem work is that you look at the target's AC, the attackers THACO, subtract one from the other which produces a modifier. A higher modifier is worse. Then you roll 2d6, add the modifier and look it up on the Battlesystem chart. This produces the number of hit dice of damage.
Battlesystem abstracts damage and hit points into Hit Dice. So an Orc has 1 HD, a Ogre has 4 HD and so on. They reached back to Chainmail for the inspiration on this.
Then you shift to a higher dice column if you have a damage bonus. So a unit doing 1d8+2 would start with the d8 column and shift over to the d10 column and then the d12 column. Multiple attacks each look up their damage separately and are added together. For heroes each HD of damage inflicted on them does 4 hp.
As pointed out earlier the system is built when there is 10 individuals per figure. When you have 5:1 or individual a +modifiers is added on top of everything else. For individuals this is +15.
So I figured out the math for Ascending AC and using To Hit Modifier instead of THACO. It worked well in play but I had to write down a table of everybody AC and modifiers to make it go quickly. It wasn't enough to just have the stats on cards.
The battles are not as challenging as they could have been. In the first one advancing in close order was a big mistake against the fireball the parties possessed. The orcs quickly suffered morale checks, failed, and ran. The second was better as the orcs advanced in skirmish formation and the battle went as well as I hoped. The party had their backs on the wall and were bloodied but they managed to execute a plan that saved the day for them.
I have to save for the OD&D fighter, mass combat is where they shine. Now the group had a lot of fireball runes (think scrolls) so it wasn't readily apparent. But on reflection the fighters were the ones really pumping out the damage. Especially against the one HD creatures. I think a lot of the complaints about fighters vs magic-users would disappear if mass combat was used more.
The Orc Wizard really made a difference as well. In any setting using DnD mechanic having heroes is critical. Heroes will need some forces but there are cases, this this one, where a group of only heroes is enough to turn back the orcs.
Two other things I overlooked. The Orc wizard's magic items, just plumb forgot to use them. Although after the attack of the knight and the fire elemental probably wouldn't not have made any difference. Then I forgot to add Warg Riders. The big impact of having them is that they are not considered 1HD creatures as the mount and rider combine to produce the final stat card.
Timewise both battles did not much longer than a regular OD&D combat which was a pleasant surprise. With experience it would probably take just as long. One time saver is that you treat each unit (with 4 to 15 figures) as a single entity..
Speaking of unit cards you can download the ones I made from here.
Now that I have run Battlesystem I am really impressed with it. At its heart it uses a Binomial distribution chart to quickly resolve d20 combat. This means it can be applied to ANY edition edition of DnD. Something I intend to try with the Dungeon Crawl Classics RPG.
The player complaints was the switch to 2d6 low, and the fact we were using counters. Unfortunately any method to use a d20 roll high would be cumbersome. And any simple method would not be accurate or fair. Binominal distribution allows to calculate the odds of success over many trials (i.e. rolls) . The result is a bell curve which means multiple dice need to be roll. Battlesystem elected to use 2d6.
I hope you find this informative and give 1st edition Battlesystem a try.