This was an amazing follow-up to "Armageddon"! Our protagonist and group survive the incursion of hostiles, regroup and keep on keeping on. They do more reconnaissance and perform a fee rescue, one of which involves military personnel. This eventually leads to our protagonist returning to active military service and becoming the ranking officer on the ground, which put him in charge of many soldiers and civilians. There is a small contingent of military (on destroyer ships) still active and trying to do what they can to protect the remaining living and take out the threat of the dead.
After a search mission gone bad, our protagonist is separated from the group, on his own, injured and on foot, hundreds of miles from home. It's a harrowing experience and he almost dies several times. Then his luck changes and he gets help from an unknown group, with experimental tech. He picks up an ally along the way, and they work together to get back to safety.
He makes it back to the bunker after being gone for 45 days. Once back and rested they learn that the group that 'helped' him get back home, had ulterior motives, and the bunker comes under siege. They are able to escape and get evacuated to the war ships. There we learn that they are planning a mission to China to retrieve patient zero--because of course it always starts in China! And this all started because scientists found a non terrestrial vessel in a block of ice and just had to investigate it. They didn't follow protocol, this the outbreak of an unknown disease that brings the dead back. *sigh* That explanation was unexpected, but not necessarily a bad one. At least this series gives an actual explanation as to where this outbreak came from. Now our protagonist is commissioned to the mission to find patient zero and perhaps a cure, or vaccine. Can't wait to see what happens next!