The game is a third-person shooter featuring large play areas and waves of mecha and giant insects. Players control either a foot soldier who uses conventional weaponry such as assault and sniper rifles, shotguns, and rocket-propelled grenades or a jetpack-equipped soldier who uses energy-based weaponry. Most of the game's missions are cleared by eliminating all enemies present, starting with giant ants on earlier stages and eventually progressing to giant lizard enemies. A number of vehicles such as a tank, helicopter and a hover-bike are available in some missions for players to board and attack enemies with. However, only the Storm-1 unit can use the vehicles. A total of 300 different weapons are available between the two characters, but players are limited to carrying two weapons during missions. Weapons are unlocked by picking up containers dropped by enemies. Every weapon picked up during play will add a random weapon of the character's to the selection, duplicate weapons are discarded. Armor chips and medical kits, also dropped by enemies, increase the character's maximum possible health and recover lost health respectively. There are a total of 71 missions spread over 7 environments to play through, the first mission taking place in London. Five difficulty levels are available for each mission. Half-medals are awarded for completing a mission on a set difficulty with either character. Completing the same stage with the other character results in a complete medal. Once a player has collected all the medals for every mission, "Impossible" mode is unlocked.
Reception
Global Defence Force received little press attention in the West. The few reviews the game received were generally positive; Games Asylums Matt Gander described it as "one of the PlayStation 2’s best budget buys". In Japan, Famitsu gave it a score of one eight and three sevens for the PS2 version; and one eight, one seven, and two sixes for the PSP version. The PlayStation Vita re-release of the game, published by Xseed Games and retitled Earth Defense Force 2: Invaders From Planet Space, received "average" reviews according to the review aggregation website Metacritic. Destructoids Jed Whitaker wrote that the game "has enough original content to keep it feeling fresh alongside the other recent releases in the series", and that it was "easy to recommend to Vita owners looking for some campy over-the-top action in spite of its flaws." In Japan, Famitsu gave the Vita version a score of three sevens and one nine for a total of 30 out of 40. During D3 Publisher's simple series awards 2007, the title received a platinum prize for selling more than 200,000 copies in Japan during the 2006 fiscal year. It was the only title in the range to reach this volume of sales.
