#Retro #TravellerRPG #Wargame #AAR – Invasion: Earth – The Final Battle of the Solomani Rim War (Game Designers’ Workshop, 1981)

BLUF – Game mechanics are deceptively simple but through play one discovers it’s not necessarily combat that is important but executing an invasion plan that requires proper logistical planning and bringing the right forces to bear at the right time and place versus a stubborn defense that must know when to ‘hide’ and fight another day.

NOW THAT I ACQUIRED A GRAIL WARGAME IN THE TRAVELLER RPG UNIVERSE, it was time to play it. Invasion: Earth – The Final Battle of the Solomani Rim War (GDW, 1981) takes place in the Third Imperium setting of the Classic Traveller RPG. The game depicts the invasion of Earth (Sol) by the Third Imperium in the year 1002 (the 55th or 56th Century compared to today). Interestingly, Invasion: Earth (IE) is a ‘historical’ game in the Traveller RPG line as the invasion takes place just over 100 years in the past of the default setting (years 1105-1107).

Physically, Invasion: Earth is a small game more suited to a folio than a box. The map is small, 16″x21″, which covers not only Sol but also holding boxes for different space locations as well as the terrain key. The game includes 480 counters although half are game markers leaving only 240 pieces for actual combatants. Yes, the counters are small – 1/2″ sized – and challenging to this grognard’s eyes. This is a game where a magnifying glass and tweezers to move stacks is required!


The rule book is just as small – 16 pages – and I previously talked about what I like about it. Although Invasion: Earth is both a space battle and ground combat game, a scenario will see mostly ground combat. As I played my first game of Invasion: Earth I discovered the game proceeded in noticeable ‘phases’ where the players face different challenges and are forced to make sometimes painful decisions.

Phase I – The Space Battle

The Imperial player starts in the Out-System Box and has to ‘jump’ into the Sol System. The arrival area is known as Deep Space. Since the Solomani ships cannot ‘jump’ the Out-System Box effectively serves as the ‘off-map’ assembly area for the Imperial player. The Solomani player cannot set up in Deep Space but instead is limited to Far Orbit (which includes Luna) and Close Orbit – the only orbit which interfaces with the planet. In Phase I the Imperial player has to push aside the Solomani space forces to get to Close Orbit and land troops on the planet.

Invasion begins….

The problem is those pesky Solomani ships and boats. All ships and boats (non-FTL capable ships) have three ratings – Attack Factor / Bombardment Factor / Defense Factor. However, using the right ship/boat in the right space combat is important. In combat against starships you use the Attack Factor. Combat against boats and ground units use the Bombardment Factor. Each has its own Combat Resolution Table (CRT) where losses are expressed in ‘hits’ or Defense Factors that must be eliminated. This means the first decision the Imperial player faces is how to divide his force to attack defending ships and boats because each squadron can only attack one or the other. Space Combat continues until one side is eliminated or disengages. Ships that disengage move the the Deep Space box where they go into ‘hiding.’ Additionally, if there are no Imperial ships in Close Orbit, those pesky System Defense Boats (SDB) can hide in the ocean. Hidden units have advantages later during the actual Invasion and Occupation phases of the game.

Phase II – Advance Base

For the Imperial player, movement to/from the Out-System can only happen once a turn. This means to bring reinforcements from the Out-System effectively takes two turns. However, if the Imperial player lands a Base on Luna, it becomes an advanced staging area. The challenge for the Imperial player is balancing a need to invade Sol and consolidate forces on Luna. Sounds easy until you take into account Transport.

Different space units have different transport capacities. Ground units have different strength based on their size. Generally speaking, an army is 5C (500), a corps 1C (100), a division 20, a brigade 10, and a regiment 5. Bases (supply points for the Imperial player) are the equivalent of 1C. Different ships can transport different ground units; an Assault Carrier (AR) can carry 6C, a Battle Squadron (BR) carries 20, and a Cruiser Squadron (CR) carries 5. Each ground unit must be carried by a single naval unit – there is no combining 4x CR to carry that 20-Factor division. So the Imperial player has to figure out the logistics game of what ground unit is carried by what squadron. This challenge is not only present in this Advance Base Phase but throughout the game. It becomes even more challenging after Turn 2 when two of the four AR in the game are withdrawn.

Phase III – Invasion!

The invasion of Sol can take place in parallel with the consolidation of an advance base; indeed, the Imperial player is almost forced to execute these two in tandem given the need to achieve victory in the least amount of time. In Invasion: Earth there is little differentiation between ground units but the few differences there are make a big difference.

When landing, eligible defenders roll on the Surface Bombardment Table to see what percentage of the landing attackers are destroyed. The defender totals their Bombardment Factors and rolls single d6 on the column that is closest to, but not more than, that value. The roll is modified by two qualities of the attacker – Tech Level and unit  type.


Tech Level (TL) is a key concept in the Traveller RPG setting. The higher the TL the more advanced the unit is. TL is one of the most important factors in combat (more on that later) but in an orbital assault units of a lower TL have a -1 DM to the defenders attack roll, meaning they are likely to suffer MORE casualties. Unit type also plays an important roll. Performing an orbital assault with a unit other than a Jump Troop or Marine is a -3 DM (!). The last thing an attacker from orbit wants to do is land a low-tech, non-Jump or Marine unit against a determined enemy! This means the Imperial player should try to lead the orbital assault with those (few) Jump or Marine troops – assuming they are available and loaded properly on the lead wave.

Phase IV – Occupation

Assuming the Imperial player is able to land troops, in order to win they must control, through occupation, all but 10 Urban hexes on Sol. Control of an Urban hex is through Garrisons. To Garrison a hex it must be either occupied solely by an Imperial unit or within the Zone of Control (ZoC) of an proper Imperial unit and NOT in the ZoC of a Solomani unit. In practice this means the Imperial player will have to slog through many Solomani defenders. To do so will require a thorough understanding of Supply, what makes units different from one another, and Replacements.

Supply for the Solomani player is easy – any Urban or Starport hex is a source of Supply. The Imperial player on the other hand must bring their own supply with them in the form of Bases – that cost 1C to transport – meaning only the (few) AR can deliver them to the surface. Bases also make great targets for the Solomani player. Units that start the turn out of supply may not attack and can defend with half their current value.

At first glance, the ground combat system looks rather like a Lanchester Attrition Model that Trevor Dupuy would be proud of. Combat is a simple odds roll with results expressed in Percentage Loss. The stacking rules allow up to 1000 factors (!!!) in a single hex. So why would one want to play this uninteresting attrition game?

Well, because of the few unit types and Tech Level.

There might not be many different ground units in the game, but the few differences are very important:

  • Army, Corps, and Planetary Defense units ONLY extend a ZoC
  • Armor units have their strength doubled in attack or defense
  • Elite units have their strength doubled (this can stack with the Armor bonus)
  • Tech Level differences are COLUMN SHIFTS on the CRT
  • Mercenaries with over 50% losses have their attack strength halved (they are in it only for the money)
  • Commando units ignore enemy units and ZoC during movement and are always in Supply making them the ultimate infiltrators
  • Guerrilla units are attacked with a +3 DM when hiding.
An Imperial TL14 Elite GravArmor Division takes on a Solomani TL11 Infantry Corps. 1:5 odds? Not so fast….

In keeping with a core tenet of the Traveller RPG the greater the TL difference the more the hurt! Assume a TL14 Imperial Elite Tank Division (20-14) is attacking a defending TL11 Solomani Infantry Corps (1C-11) as shown above.

  • Imperial attack 20×2 (Armor) x2 (Elite) = 80 vs 100 (1:1.5 SHIFTED UP 3 columns to 2:1) – 8 in 11 chance of 10-70% losses
  • Solomani defend 100 vs 80 (1:1 SHIFTED DOWN 3 columns to 1:3) – 3 in 11 chance of 10-20% losses.


At the end of each calendar quarter, a special turn is executed. This is where both sides can receive Replacements in the form of Replacement Points (RP).

  • Solomani – Accumulate 1x RP for each ungarrisoned Urban hex on the map (there are 61 Urban hexes at the start)
  • Imperial – RP comes in the form of a Wave of 100 RP.

Each RP can rebuild a single ground unit combat factor. It takes 100 RP for the Imperial player to build a Base. The Imperial player can also use a Wave to replace any three eliminated naval units. The Solomani player can start to rebuild an SDB unit at a Starport for no RP but it will not be completed until the next quarter’s special turn (assuming it was not destroyed by being overrun or bombarded). There are additional rules for Emergency Replacements which can be called upon outside of the special turns but are not as plentiful.

End State – Victory

Victory in Invasion: Earth is not based on playing a set number of turns. Instead, in each end of quarter special turn Victory is checked. The Imperial player always has the option of abandoning the invasion which awards the Solomani player a Major Victory. If not, play continues every quarter until the Solomani have 10 or fewer Urban hexes ungarrisoned by the Imperial player. At this point, the Imperial player is awarded 10 VP. Modifiers are then applied:

  • -1 VP for each quarter of the invasion
  • -1 for each Replacement Wave taken by the Imperial player
  • +1 if all Solomani surface units eliminated
  • +1 if all Solomani naval units eliminated.

The Level of Victory Table is then consulted:

  • VP 7+ > Imperial Decisive Victory
  • VP 4-6 > Imperial Major Victory
  • VP 1-3 > Imperial Marginal Victory
  • VP 0 or -1 > Draw
  • VP -2 or -3 > Solomani Marginal Victory
  • VP -4 or less > Solomani Major Victory

In order to win, the Imperial player must be both quick AND efficient with their resources; making as much as they can with the assets they have on hand. The Solomani player benefits from a long, drawn out war of attrition and hiding some units to prevent their destruction (a Fleet-in-Being?).

In my game, the Imperial player did not achieve the Standard Victory (10 VP) until the fifth quarter of play (-5 VP). The Imperial player also took 3x Wave of RP (-3 VP). Not all Solomani ground forces were eliminated and there was a lone Solomani CR that hid in Deep Space the entire game . This was enough for an Imperial Marginal Victory – and boy did it feel marginal!

AAR – or – After Action Reaction

Invasion: Earth turns out to not be the game I was expecting. Looking at the box and the first pass through the rules thought I saw a somewhat staid game with a very old-fashioned combat model that didn’t look like a vision of the future but rather a rehash of the past. Instead, what IE delivers is a master-class lesson on opposed landings and shows a vision of the future where timeless lessons of amphibious landings are applied to orbital assaults. The rules drive the players to carefully husbanding their resources and allocating forces with thought. Indeed, I had not expected a game that appears this simple to be this deep in the decisions it forces upon players.


I note that Invasion: Earth was published in 1981, a year before the 1982 Falklands War where the Royal Navy and British ground forces were challenged to figure out how to carefully load troops and logistics on few amphibious ships and execute an amphibious landing far away from their bases. The British also faced a narrow timeline for action being called upon to invade and retake the islands before the winter.* Invasion: Earth and the Falklands War are eerily similar, and even more eery when one considers IE came before the Falklands War. Then again, maybe designers Marc Miller and Frank Chadwick were just expressing age-old, never-changing lessons of amphibious warfare in this paper time machine.

If so they did a very good job.

*For a good modern wargame on the Falklands War that is soloable, I recommend Mrs. Thatchers War from White Dog Games.

Mind the gap – the #wargame paper time-machine of Tokyo Express (Victory Games, 1988)

JAMES F. DUNNIGAN, ONE OF THE FATHERS OF WARGAMING, is credited with stating that wargames are a “paper time-machine” (1). This is great, but there is actually alot missing here. Let’s look at the full quote which opens Chapter 1 of Dunnigan’s seminal work, The Complete Wargames Handbook:

What is a Wargame?

A wargame is an attempt to get a jump on the future by obtaining a better understanding of the past. A wargame is a combination of “game,” history and science. It is a paper time-machine.

The Complete Wargames Handbook, 3rd Ed, 1.

This week as part of my 2019 CSR Awards Challenge I replayed Tokyo Express (Victory Games, 1988). At the same time, I took delivery of a new book, Learning War: The Evolution of Fighting Doctrine in the U.S. Navy, 1898 – 1945 by Trent Hone (2). Put together, the game and book got me thinking about wargames and what we learn from them.

Much has been written about the role wargames played in educating the US Navy before World War II. Hone tells us how war gaming “encouraged experimentation with new tactical approaches and improved the ability to assess them.” He goes on to state:

The primary purpose of the games, or “war problems,” was to further the education of officers. They gave practice at applying the principles of war, encouraged critical thinking, and provided practical training in the art of command.

Learning War, 98.

I can see that. I definitely agree that wargames are excellent at applying the principles of war, making me think critically, and in a loose fashion exercise command. But it’s not perfect. In his chapter “Heuristics at Guadalcanal”, Hone discusses the Battle of Tassafaronga. One passage in particular jumped out at me:

Prior to the battle Rear Admiral Kincaid had assessed the lessons from earlier engagements and developed an aggressive plan incorporating them. He instructed his destroyers to press ahead and attack them from close range with torpedoes; the lead destroyer would use an SG radar to develop a clear picture of the action and guide the others to the launch point. Cruisers would remain distant, far from the threat of Japanese torpedoes; they would use radar-assisted gunfire as their primary weapon. Like Lee, Kincaid refused to employ Scott’s linear formation.

But Kincaid was wrong about Japanese torpedoes. He expected them to be similar to the Navy’s own. Since ten thousand yards was beyond their effective range but was also the maximum range of radar-directed cruiser gunfire at the time, Kincaid instructed the cruisers to engage from that range. He expected in that way to stay out of “torpedo water” while inflicting maximum damage to the enemy.

Learning War, 203-204.

As we know, the battle did not turn out well for the US Navy. As Hone writes, “Wright’s cruisers opened fire moments after Cole released his torpedoes. Tanaka’s destroyers had already seen Wright’s ships and were setting up their own torpedo attack” (3). James D. Hornfischer, in his book Neptune’s Inferno, called the Japanese attack, “one of the most lethal torpedo salvos of the war” (4). Minneapolis and Pensacola were hit; New Orleans’ bow was blown off. Northhampton was sunk (5).

Norman Friedman, in his book Winning a Future War: War Gaming and Victory in the Pacific War (Washington DC: Naval History and Heritage Command, 2017) writes in his concluding chapter “Games versus Reality in the Pacific,” that wargaming for the US Navy before World War II had three possible functions:

  • To explore possible wartime situations in ways full-scale exercises could not
  • To teach students how to fight
  • To understand or even predict the behavior of foreign powers (6).

Friedman points out that for the first function military judgement based on experience could often foresee outcomes but not when entirely new technology was involved. This ties closely with the third factor because it required players simulate alien ways of thinking (7).

Just how does this get recreated in a wargame? The problem is that we wargamers often “know” that Kincaid’s initial deployment and battle plan at Tassafaronga is “flawed” because, unlike Kincaid, we know about the Japanese Long Lance torpedo. Therefore, wargamers can consciously (and more often unconsciously) act to avoid the danger. This is what designer Tetsuya Nakamura terms “the hindsight gap:”

The hindsight gap arises because people living through real history do not know the results of their actions, but a player in a tabletop simulation game is aware of these results. For example, the French army believed that tank forces could not pass through the Ardennes Forest, but German Panzer forces did exactly this in 1940. In another instance, the Imperial Japanese Navy was ambushed by the US Navy at Midway in 1942 because they believed there were no US aircraft carriers there. But in a tabletop simulation game, we already know that there are hidden US aircraft carriers at Midway, so players will never fall victim to such a surprise attack.

Tetsuya Nakamura, “The Fundamental Gap Between Tabletop Simulation Games and the “Truth.” Published in Zones of Control: Perspectives on Wargaming, Edited by Pat Harrigan & Matthew G. Kirschenbaum (Cambridge: MIT Press, 2016). 43.

In many ways Tokyo Express is an excellent combination of game, history, and science. What really sets it apart is how the Enemy AI overcomes some of the hindsight gap. Unlike a game such as Command at Sea (Admiralty Trilogy Group) with its scenarios that try to faithfully recreate the battle, the Enemy AI in Tokyo Express can operate in “unexpected” ways. Be it the arrival of unexpected forces or enemy operations in ways that are plausible but not historically exact, the Enemy AI in Tokyo Express can teach a player that has the benefit of the hindsight gap. The science of the Enemy AI in Tokyo Express gets us past the hindsight gap. In turn, Tokyo Express gives us a better understanding of the past making it a better game for getting a jump on the future.


  1. Dunnigan, James F. The Complete Wargames Handbook (3rd Ed. Lincoln, NE: Writers Club Press, 2000), 1.
  2. Hone, Trent. Learning War: The Evolution of Fighting Doctrine in the U.S. Navy, 1898–1945 (Annapolis: Naval Institute Press, 2018). The Chief of Naval Operations (CNO), Admiral John Richardson, recommended Learning War to new Admirals, Retired Flag Officers, members of his staff, and other naval officers. It reflects the strong emphasis he is placing on command in 2018 and it is now part of the CNO’s reading list. ( There is also another notable wargaming book on the list. See Philip Sabin’s Simulating War: Simulating Conflict through Simulation Games (London: Bloomsbury Academic, 2014)).
  3. ibid, 204.
  4. Hornfischer, James D. Neptune’s Inferno: The U.S. Navy at Guadalcanal (New York: Bantam Books, 2011), 390.
  5. Hone, 204.
  6. Friedman, 161.
  7. ibid.

Feature image Battle Display from Tokyo Express.