Team Fortress 2 Invasion is the successor to Brotherhood of Arms, and the predecessor to the final Team Fortress 2. It is presumed to have been developed from about 2002 to 2003, since most of the leaked files are from around this time.
Team Fortress 2 Invasion is a "steampunk" first-person shooter developed by Valve Corporation, one of the proposed sequels to Team Fortress Classic. Like with multiple other early designs of TF2, it was cut for varying and unclear reasons.
There are two teams, the Humans and the Aliens. Gameplay is primarily based in collecting resources, which are gained through collecting from Resource Pumps, kills, and destruction of enemy buildables.
Other gameplay features include controllable Resource Zones that housed resources that could be harvested using Resource Pumps. You could also build defensive objects such as tunnels, and towers.
To win a round of Invasion, you either destroy all of the enemy team's Respawn Stations or harvest the most resources. These two factors would be compared between teams at the end of an Act, and would be used to determine what team won.
There are several classes present in this incarnation, including:
In 2003, a German hacker gained access to and released the password for Valve's file server and took Valve's development files, which reportedly included a full build of TF2. In the leaks, he unintentionally released some of what he had to the public, which amounted to the Human and Alien Commando models and the full source code at the time.
Although the only two models that remain released to the public to this day are only the Human and Alien Commando models, a look at the source code clearly hints that many more models were done during the development of the game. Such model references, include, for example:
2012 Source Engine LeakEdit
In Adamix's 2012 leak of the Source Engine's source, there is still a large amount of code leftover from this incarnation of TF2. The code is changed and modified, showing that Invasion was worked on a little after it's code was leaked.
Moby Francke, ~2005-2008Edit
Sometime between April 4th, 2005 and June 14, 2008, Moby Francke created a new portfolio to replace his earlier HTML-based one. It is not entirely known what was contained within, as the Flash-based introduction page seen at the start prevented web crawlers from getting past it.
Though normal web-archiving services failed to grab it, the Half-Life wiki has some images from before the later portfolio with "mobyfrancke.com" as the stated source. A few of these are not seen in the later portfolio.
Robin Walker E-MailEdit
On June of 2016, Robin Walker was contacted about this particular set of sketches, and revealing that this release is from an earlier "Humans vs Aliens" stage:
With the Uber update came a new site with several additional sections, including a new art section. Among the concept art placed there is some (at the time) new Invasion-era concepts, with some informative filenames. These reappear in Moby's portfolio, but the filenames here aren't lost, and the comments on the commando aren't present on the Moby counterpart.
Moby Francke, 2013Edit
Around July of 2013, Moby Francke left Valve and overhauled his portfolio with several bits of new art, with among them several early Invasion-era concepts. The art was mainly silhouettes and concepts for human characters, with a few concepts for larger aliens included.
Chuck Jones, 2014Edit
In August of 2014, Chuck Jones posted a large collection of concept art from this version of TF2, which depicted a multitude of weapon designs with a cyberpunk theme. Unlike Moby's exclusive releases of character concepts, his varied art depicted various, environments, renders, and even included a partial screenshot, with a wealth of informative captions included with the gallery.  A snippet of text about the project was included alongside:
Early TF2 explored multiple pathways in art direction and game design. It first started with Modern warfare TF2 then to Space TF2 with aliens. After more exploration, War of the Worlds TF2 was getting some traction. We had a steampunk flair to all the designs. This version had a truck with a big battering ram driving around. And we were using Striders from HL2 as the Tripod aliens.
From around 2006 to 2008, Team GabeN actively attempted to remake this game from the code. A direct release was never made, but a large amount of information about it is present on their wiki. The TF2 page was last edited in 2008, so it can be presumed that the project fell into inactivity around that time. An early build from 2006 called the "X-Mas build" is the only build that was ever released, which is incredibly early and unpolished.
- Project Beta Build
- A modification of the GabeN build with a new custom 2fort-based map, and some other modifications. It is available on Project Beta.
- Mine / TFI Team
- A modification of the GabeN build with some improvements, started between 2015 & 2016. The first release was on October 1, 2017, and development is ongoing.
A port of TF2 invasion's source code to Source SDK 2013, led by hogsy. It can be found here, and downloaded here. It is currently unclear whether the project is in continued development, as as of October 2017 the Github page states the last commit was on "Feb 20".
- Team Fortress: Invasion (NextWizard)
The Axel Project's Invasion Edit
A few unlisted videos have been discovered of a build of Invasion being worked on by the team behind the Axel Project. The only videos of it shows the sentry gun and resource pump in action, but nothing else. It was never officially released or mentioned besides these two unlisted videos.
- ↑ Section based on GabeN wiki
- ↑ http://half-life.wikia.com/wiki/File:Medic_concept_1.jpg
- ↑ http://half-life.wikia.com/wiki/File:Armor_concept1.jpg
- ↑ http://www.tfportal.de/?site=news_details&id=1185
- ↑ http://www.tfportal.de/?site=news_details&id=1196
- ↑ The earliest capture of mobyfrancke.com is in 2013.
- ↑ http://mobyfrancke.com/
- ↑ http://www.chuckejones.com/valve.html
- ↑ http://www.teamgaben.com/gaben/index.php?title=Team_Fortress_2_%28GabeN%29&action=history
- ↑ https://www.moddb.com/games/team-fortress-2-invasion