Blackmoor grew from a single Castle to include, first, several adjacent Castles (with the forces of Evil lying just off the edge of the world) to an entire Northern Province(s) of the Castle and Crusade Society's Great Kingdom.
Dave Arneson, The First Fantasy Campaign (1977)
The first major section in JG 37 "The First Fantasy Campaign" provides information used by Dave Arneson in running what appears to have been a Napoleonic-style wargame as part of his Blackmoor campaign. While fascinating, I probably wouldn't have led with it.
The information presented can be used in a OD&D campaign set in Blackmoor, but would be more fun to run as an actual wargame. The mechanics of play are at least partly based on Chainmail, as discussed by Daniel Boggs in his post Blackmoor as a Chainmail campaign.
The Great Invasion
Arneson provides details for "Part A, Scenario III", stating that details for the previous two scenarios were lost. These likely involved the first two "Coot invasions", for which a basic outline of events is known.
Illustration by Larry Elmore.
The 1st year of the Blackmoor campaign involved a defense of the town against the forces of the Egg of Coot, after which the character played by David Fant became the new Baron of Blackmoor (for an interview with Fant, see this post on Daniel Bogg's blog "Hidden in Shadows").
Events of the campaign were chronicled in Arneson's "Corner of the Table" newsletter, and the "Blackmoor Gazette and Rumormonger". By spring of 1972, the players were more interested in exploration of the dungeons beneath Blackmoor Castle, than defense of the town itself.
As a result, the first Blackmoor campaign drew to a close by the summer of 1972, with victory going to the forces of the Egg of Coot. The player's characters were exiled, and the campaign entered a new phase (see "Blackmoor, in the Era of Loch Gloomen").
The 2nd year of the Blackmoor campaign involved a turncoat character played by Kurt Krey, former captain of the guard in Blackmoor. By this time, games were being held at St. Thomas College. The players were ultimately victorious, and were awarded fiefs.
Which finally brings us to "The Great Invasion":
The entire 3rd Year of the Blackmoor Campaign was to be part of a Great War between the Good Guys and the Bad Guys.
I believe this roughly coincided with the third year of actual play, dating from 1973-1974, with "The Great Invasion" representing the third Coot invasion.
Orders of Battle in the The Great Invasion (the Third Coot Invasion)
David Wesely recently commented on a post on The Ruins of Murkhill blog, regarding The Great Invasion. The Earl of Vestfold was played by Greg Svenson, the Horsemen of Peshwah by Ken Shepro, Bramwald by Duane Jenkins, the Wizard of the Wood by Peter Gaylord, and the Monks of the Swamp possibly by Steve Rochford.
It's interesting to note that Blackmoor itself, having been captured by elves after falling to the Egg of Coot, is not counted among the Good Forces, but is listed under the Neutral Forces, together with the Wizard of Mi-Karr, named after Mike Carr, and the Regent of the Mines, played by Steve Lortz. I'm not certain whether any of the Evil Forces were run by players.
The Original Price/Unit Ratio List
Daniel Boggs points out many similarities with Chainmail for Unit Types, Costs per Man, and Weapons in Blackmoor as a Chainmail campaign. It's interesting to note that many of the Weapon Costs in GP are comparable to those in OD&D.
Additional Weapon Cost/Limit covers missile weapons, and Additional Price Lists includes Weapons, Armor, Transportation (wagons, ships, horses, and even tarns), and Heavy Construction (including for Standard Castle Types, as depicted below)
Standard Castle Types, from JG 37 "The First Fantasy Campaign"
There's also a listing of investment areas (discussed in more detail in its own section, below). Finally, Personnel Costs (in GP for 1 Year's Pay and Upkeep) are given, as explored in Blackmoor Taxes, Living Expenses and the Support and Upkeep of Hirelings in OD&D.
The next three sections cover additional material necessary to run "The Great Invasion" (outlined, below). The easiest way to do so, nowadays, might be to use the Dominion and War Machine rules from the D&D Companion Set (1984).
The Later Prices Lists
Earl of Vestfold, including one city (Tonisberg, 15 villages), two small forts (1 village each), and Tribute (all of the Neutral Forces listed, except the Regent of the Mines, are considered minor holdings of the Earl of Vestfold). Trade with Great Kingdom. Rules for Wizards and Magic.
Northern Lords (Sea Raiders) aka Skandaharians, including two cities (4 villages each), and 10 villages. Trade with Maus, Egg of Coot, Great Kingdom, and Other Areas. No Magic.
City of Maus, including one city (10 villages), and 20 villages. Trade with Great Kingdom, Egg of Coot, and Skandaharians. Rules for Wizards and Magic. Also includes price list for "Reinforcements from the Grand Kingdom" (arrive through Special Cards).
Regent of the Mines, including one city. No Trade or Magic.
Duchy of Ten, including three cities (4 villages each), and 12 villages. River Trade to North, to Egg of Coot, and to Grand Kingdom. Rules for Wizards and Magic.
Minor Holdings of Duchy of Ten - Nomads of Ten, including one city (4 villages), and 12 villages. No Trade. Rules for Wizards.
Egg of Coot, including one city (10 villages), and 12 villages. River Trade to North, with Duchy of Ten, and with Skandaharians. Rules for Magic.
Roads, Bridges, Canals, Inns
Hunting, Armories and Animal Branding:
These come under the heading of Hobbies (see Player Motivation), and may be treated as such. Just a few notes added to those of D&D are that each should have a separate building to house it's activities, have present a Specialist of the desired type, and get regular funding (payment) for goods and services produced.
Ship Building, Farming, Fishing
Trapping, Tourism, Arrival of New Persons
Land & Sea Trade
Rules are given for Merchant Ships and Wagons, Trade goods, etc. as well as a Price List (pertaining to Investments and Trade).