Prove the existence of extraterrestrial life...

Accept unofficial assistance in completing your mission...

Protect the nuclear plant from an alien attack.

Come across an extraordinary device...

Get rewarded appropriately for your hard work.

"I told you they'd be back!"

"If I had a nickel for each time this happened at the nuclear plant, I’d have two, which isn’t a lot but it’s weird that it happened twice ..."

Engage alien armor elements in a large tank battle.

Fight delaying actions to slow the alien advance towards populated areas.

In a last stand, grind the alien advances to a halt...

The genie is out of the bottle...

Throughout the duration of a mission chain, suffer fewer casualties than the alien forces.

Complete an entire mission chain without losing a single vehicle...

Complete a mission without a single casualty!

"I'm a strike squad all on my own."

Abuse your air superiority by carrying out a total of 100 airstrikes on enemy positions ...

Call in a total of 1000 artillery strikes on enemy positions ...

Wipe an enemy squad of at least 5 units with a single strike!

Participate in the defense of the airport, at least for a period of time ...

This is ordinarily a felony offense, but ...