- Easy: Soldiers only get knocked out.
- Normal: Soldiers get knocked down when "dead" and slowly bleed out, only being insta-killed by high-damage critical shots. (This adds another gameplay element where players can risk their men to recover and heal their wounded.)
- Hard: Soldiers die.
- Easy: Aliens rarely infiltrate. If you kick their asses, the country will renege on their pact and rejoin the UN.
- Normal: If you kick their asses, the country will renege on their pact and rejoin the UN. (This makes infiltration a reversible event, allowing players who want to dig their heels in to set the pace of their own campaign.)
- Hard: Alien infiltration as normal.
- Easy: You will be notified of alien missions, even if they are outside of radar range.
- Normal: You will be notified of important / long alien missions, even if they are outside of radar range.
- Hard: You will only be notified of alien missions after they happen unless they are within range of a friendly base (forces you to patrol aggressively).
- Easy: Aliens will continue with missions as in the original.
- Normal: Aliens will prefer to pick areas of operation where you have had the relatively least amount of successful interceptions/missions. Aliens will search for your bases in areas where you have had over [threshold] successful missions.
- Hard: Aliens will aggressively search for your bases. Aliens will attempt to stage simultaneous operations attacking places where you are entrenched while performing other important missions (infiltration, terror, etc.) in areas where you have little presence. Aliens will not be slowed down for a time by shooting down their ships.
- Easy: Large starting base with everything you need, ready for expansion.
- Normal: Starting base has all the essentials, maybe not everything you need for a running start.
- Hard: You begin with only the bare essentials: living space for your troops, just enough storage to hold a little gear and a hangar.