State of Decay has been an enormous success for Undead Labs, and the studio is preparing to deliver some oft-requested features in a new expansion. Lifeline will give players new characters, a new map, and new challenges.

We went hands-on with Lifeline at PAX to experiment with the new weapons, zombie sieges, and some of the new base upgrade options. The second major expansion to State of Decay will task players to rescue civilians as part of the military.

Time is a factor in Lifeline, and players will need to get survivors back to base and defend the walls against a zombie surge when helicopters come to airlift people out. The choppers are a source of minor supply drops too, so you won't be left too depleted after fending off the undead.

In order to fortify your location, you'll be able to create minefields and craft distraction canisters. These compressed oxygen canisters have fireworks attached that can be set off by firing at them. After a while (or by another well-placed shot), they'll detonate and take any nearby zombies with them. You don't have to hang out at base when the helicopter comes, but making that choice means you'll likely be sentencing some of your party to death.

You'll also have a variety of military bombardments available to you. Air strikes, mortar shelling, and other abilities are all at your disposal from the start of the game. Unfortunately, things are deteriorating at headquarters, and you'll slowly lose these perks as the game continues. You can get them back by scavenging for military gear at abandoned outposts or private military company offices. 

You can upgrade your base in a few new ways. The latrine will keep your party from becoming ill (and, yes, you'll need to assign someone to clean it). A workshop extension will allow you to reload ammo, essentially converting bullets from one type/size to another.

The ops center gives players greater control of what happens when they're away. It allows you to issue orders to your party so your time outside the base doesn't mean wasted effort at home.

With the release of Lifeline, all State of Decay players will be getting one of most requested features. Pick-up trucks can now carry six rucksacks. On foraging missions, you'll be able to load up more supplies before heading home. Once you do return to base, the trucks will automatically unload and your new goods will be in the stash.

Lifeline will be approximately four to six hours of content, but with two different NPCs trying to convince you to approach your mission in opposing manners, there's room for replay. State of Decay Lifeline will be out in early June for PC and Xbox 360. For more, check out our review of the base game.