Almost every aspect of the original game is altered, creating a longer, more complex campaign that presents players with more strategic choices and customization options.

The player directs the organization's research and development, manages its finances, and controls its soldiers in combat.

The developers announced in July 2015 with beta 15f2 that they had finished adding new features, and that any future releases would only correct bugs or balance issues.

At the time that it exited beta, the mod's development was led by four core members, JohnnyLump (John J. Lumpkin), Amineri (Rachel Norman), XMarksTheSpot, and Ellatan (Alex Rozenfeld).

[6] First and foremost, the mod invites you to struggle through a longer, harsher campaign, but provides you with some new options to endure the prolonged alien assault.

The aim of the Long War mod is, in the words of its developers, to create "much deeper strategic and tactical play and a greater variety of problems to throw at the player".

[12] Many of the mod's key features, including the increased number of soldiers and the lengthened campaign, first appeared in version beta 1.9, which was released in mid 2013.

Shortly after Enemy Within released, Amineri and XMarksTheSpot completed development of a Java-based tool called upkmodder that allowed the team to more effectively manage and implement the changes made by the mod.

The combination of fatigue and much longer injury times requires players to maintain a larger number of soldiers.

Over the course of the game, both the aliens and the EXALT paramilitary group introduced in Enemy Within conduct their own research, granting their units new abilities.

It is difficult to halt their research completely, as the aliens capture a council nation early in the game and will occasionally launch missions with vastly superior forces that the player does not have a reasonable chance to defeat.

The mod does add special missions that the player can launch to re-take council nations that have fallen under alien control.

These choices affect soldiers' damage and movement compared to the assault rifle from the base game.

XCOM 2 lead producer Garth DeAngelis said "It's unbelievable what they did" and called it his "go-to recommendation" for hardcore fans.

He called the base game "basically a 20-hour tutorial for The Long War",[14] which Chris Bratt of Eurogamer considered an exceptionally strong recommendation for the mod.

Wired praised the amount of content added by the game and called it "the absolute best way to play XCOM".

[22] Several new mechanics are added to the game, including infiltration missions that require you to send out multiple squads at once, and managing resistance havens and their members.