Deus Ex: Invisible War is a 2003 action role-playing video game developed by Ion Storm and published by Eidos Interactive for Microsoft Windows and Xbox.

The gameplay—combining first-person shooter, stealth, and role-playing elements—features exploration and combat in environments connected to multiple city-based hubs, in addition to quests that can be completed in a variety of ways and flexible character customization.

Original designer Harvey Smith directed the game, while Alexander Brandon and Sheldon Pacotti returned respectively as composer and scenario writer.

Later opinions from both journalists and the game's staff have been polarized, with several websites calling Invisible War the weakest entry in the Deus Ex series.

[1] These objectives can be completed in a variety of ways; these include using stealth to infiltrate an area, opening access points using hacking, or launching an armed assault.

Page intended to make himself a global dictator by first undermining the Illuminati by creating a pandemic to blackmail the world's elite into supporting Majestic 12, then merging himself with the artificial intelligence (AI) Helios.

[7]: 4–7  In the back-story revealed in the course of Invisible War, a combination of all three possible endings of Deus Ex took place; JC kills Majestic 12 leader Bob Page, merges with Helios, destroys Majestic 12's base in Area 51 to cripple the world communication network, then sides with the Illuminati to rebuild the world in the wake of these events.

Following the Collapse, major capitals organize themselves into city states, creating walled enclaves where the population can be watched and expansion is closely controlled.

[11] A recurring feature are "Augmentations", advanced nanotechnologies that enhance the human body; the type used in Invisible War are dubbed "biomods".

Spirited away shortly before the events of Deus Ex, Alex is raised in Chicago before being inducted into the Tarsus Academy, a group controlled by the Denton-created ApostleCorp.

[7]: 8–9, 13–16 There are several factions within Invisible War that Alex is contacted by and can choose to side with and represent different viewpoints on how humanity's post-Collapse society should develop.

[9] The two factions handling reconstruction in city enclaves are a future version of the World Trade Organization (WTO), which builds and maintains the emergent city states, acting as the de facto government body; and the Order, a religion combining concepts from multiple faiths which has gained support from people outside the enclaves and is opposed to the WTO's policies.

[7]: 10–12 [9] Note: While the general plot of Invisible War follows a distinct path, many elements such as faction alliances and character interactions are subject to the player's decisions.

During these missions, Alex learns that their biomods were created by ApostleCorp, and follows Nassif from Seattle to Cairo, which is being disrupted by fighting between the factions.

Development of Invisible War began at series creator Ion Storm following the success of the original Deus Ex.

[23] The gameplay drew inspiration from Ultima Underworld: The Stygian Abyss, System Shock, Dungeon Master and Thief: The Dark Project.

[14] Due to the game being designed for both consoles and PC players, the team wanted to minimize the number of menus to navigate, maintaining the core feeling of a first-person shooter.

[27] A multiplayer mode, which had been added to the original game via a patch, was not included in Invisible War due to time and quality concerns.

[29] Due to the limited hardware of the Xbox, the environment sizes needed to be scaled down compared to the first game, but the team tried to make the smaller areas denser, with more interactive elements.

[13][15] The AI was designed to exhibit a wider range of responses than the original game, noticing disturbances, searching environments and being able to call in reinforcements.

[33] It was later revealed that Ion Storm were struggling to work out how to port the game to PS2 given the extensive hardware differences between the three platforms, and were reluctant to do so due to these issues.

[3][54] Ryan McCaffrey of Official Xbox Magazine called the game a "brilliant RPG" despite noting its short length, praising its narrative, gameplay freedom, and in-game physics.

[1][46][47][48][49][50][51][52][54][55][56] The Xbox version was praised for its performance and graphics despite several reviewers noting distracting drops in frame rate and other technical issues.

[59] Invisible War has retrospectively been seen as the weakest mainline entry in the Deus Ex series compared to both the original game and subsequent titles.

[60][61] IGN's Brian Albert, in a history of the series, felt that its technical shortcomings and science fiction aesthetics prevented Invisible War from finding the same appeal as the original game.

[60] Neon Kelly of VideoGamer.com said the game was "widely regarded as a disappointment" due to the controversial design choices relating to its gameplay and console-focused structure.

[12] Members of staff have also spoken out against their role in the game:[18][63][64] Spector openly regrets listening to the focus testers during early development as this influenced the shift in setting,[64] Brandon faulted the sound—the more professional voice acting and sparse musical style—as being foreign to the Deus Ex series,[18][19] while in multiple interviews Smith expressed disappointment with the design decisions taken with the game despite him still liking it.

[63][65] In a conversation with Spector during a lecture at the University of Texas, Smith voiced his opinions on the game's development:[60] "I feel like we f----- up the technology management of it, [...] We had bad team chemistry.

"[60]Following the release of Invisible War, multiple attempts were made to create a third Deus Ex title, even after both Spector and Smith left Ion Storm.

Prospective development on the third Deus Ex game was halted when, following further staff departure and financial difficulties, the studio's owner Eidos Interactive closed them down in 2005.