Tier 1 mode is very tough—and it's timed! There are several ways to affect the timer. If you can kill five enemies in fifteen seconds, you freeze the timer for five seconds.
Once you have completed a mission in the campaign, you then have the opportunity to play through the mission again in Tier 1 mode.
Completion of each mission unlocks the Tier 1 mode for that mission. The Gunfighter mission where you are in the AH-64D Apache does not have a Tier 1 mode; however, all of the other nine missions where you are on foot can be played in this mode.
Tier 1 is the most difficult level in the game. While you are playing the same mission, several aspects have been changed to make for an extreme combat experience.
Whenever you take hits from the enemy, they do a lot more damage and your health is restored at a much slower rate. Therefore, it is very important to use cover since just a few hits will result in your death. If you die, you have to start the mission over from the very beginning—no checkpoints in Tier 1.
Not only is the mode deadlier, it is also more realistic. A crosshair reticule does not appear on the screen. You have to use your sights if you want to aim.
In addition, the HUD feature is deactivated, so you cannot get targeting information. Only your objective icons, icons for your teammates, and grenade indicators appear on the screen.
If that were not enough, you also can't get extra ammo from your teammates. If you run out, you will have to pick up a weapon dropped by a dead enemy and scrounge for ammo also dropped by tangos that have been eliminated.
Tier 1 is played online, even though you are not playing against anyone else. Instead, you are competing against other players for best completion times as well as other stats on the leaderboards such as head shots, knife kills, grenade kills, how much time you have frozen, longest range kill, and accuracy.
Each mission has a par time that you try to beat. There are several things you can do to stop the timer for a few seconds. These are referred to as skill kills which include head shots and knife kills.
While a few seconds here and there may not seem like much, they add up. The follow table lists the six actions that will freeze the clock as well as the duration of the freeze.
Tier 1 Skill Kills that Freeze Time
| Action | Duration of Freeze |
|---|---|
| Head shot | 2 seconds |
| Three head shots in a row | 5 seconds |
| Melee kill | 2 seconds |
| Three melee kills within 10 seconds | 6 seconds |
| Kill two enemies with a single bullet | 6 seconds |
| Kill five enemies within 15 seconds | 5 seconds |
The timer adds a sense of urgency to Tier 1 mode. However, don't let it make you rush. Since it is very easy to die, you are better off taking a bit of time and using cover.
Since you have already played the missions first, you should know where there are areas without any hostiles. Sprint through these areas to save time so you can have it for the engagements.
Since you are being cautious, also try to make your shots count. Because you get a couple extra seconds for head shots, try to kill enemies in this way. This will also help you save ammo.
Each time you complete a mission under the par time, you receive a medal unique to that mission. Once you complete all nine missions under par, you also get a tenth medal for your effort.