The Protector's War - S.M.Stirling

The Protector's War is a 2005 alternate history, post-apocalyptic, science fiction novel written by S.M. Stirling and is the second novel in the Emberverse series. The Protector's War describes the events of roughly a year, some eight years after the Change which altered the laws of physics in Dies the Fire. It describes the preparations of the Portland Protective Association for a war of conquest against the other communities of the Willamette Valley, their actions in response, and the arrival of three English refugees whose coming will help shape events in Oregon.

Plot summary:
Eight years after the Change, Clan Mackenzie and the Bearkillers, led by Juniper Mackenzie and Mike Havel, respectively, have carved sections out in the Willamette Valley for their groups. They have become bitter rivals with the Portland Protective Association (PPA), led by the Armingers. The Barons of the PPA constantly violate ceasefires between the three warring factions. During one of their raids, Eddie Liu, Baron and Marchwarden of the PPA, are confronted by a small group of Mackenzies, led by Eilir Mackenzie and Astrid Larsson. After a short skirmish, Liu leaves, again swearing revenge against the Clan. In the meantime, a small group of British soldiers, led by Sir Nigel Loring, Alleyne Loring and John Hordle, formerly of the Special Air Service, are on their way to Portland, having left England by sailing ship after being imprisoned by King Charles III. Upon arrival, Lord Arminger isolates them, and has them to help him find and obtain nerve gas. They trick him into taking a test canister of nerve gas and multiple canisters that have been neutralized. The British then defeat their guards and escape to the south.

Mike Havel, the Bear Lord and Signe Larsson Havel, his wife, go on a scouting mission to find and destroy Crusher Bailey, a PPA Associate who has been raiding and taking slaves. Crusher Bailey attempts to ambush the couple, who have been mascarading as travelers with a horse herd and a wagon of valuables. Mike and Signe retreat to the ruins of what was once a porn video store. The two prepare to fight off the bandits while they are waiting for the backup force, led by Will Hutton, to arrive. During the fight, the British refugees see the fight and attack the bandits. The bandits flee, losing most of their forces, and the British help the Bearkillers find and annihilate the enemy camp. Sir Loring and his son meet the Mackenzies during the fight, and come across their old friend Sam Aylward. Aylward was formerly a sergeant under Sir Loring, and the British troops choose to join the Mackenzies. At this point, the MacKenzies tell the story of their raid into PPA territory where after ambushing a horse-drawn train, they captured Norman Arminger's daughter and heir, Mathilda.

Soon after, Eddie Liu and his massive bodyguard Mack arrive on a diplomatic mission. After negotiating with Lady Juniper, they leave. Astrid Larsson and Eilir Mackenzie with their small band of Rangers discover an enemy camp of PPA knights. Liu returns as they attempt to warn the Mackenzies. Liu shoots nerve gas at the guards, killing all of them, and frees Mathilda. Liu searches Rudi Mackenzie's tent for a book that Mathilda gave Rudi that contains the key to PPA codes. A fight breaks out, with Liu and his troops fighting the Mackenzies and Rangers. Mack seriously wounds Rudi before he is killed by Hordle, and Liu is killed by Eilir Mackenzie. The Bearkillers arrive soon after and mop up the remaining PPA knights. Rudi is saved by Signe, who overcomes her distaste for him and saves him with a blood transfusion. The book ends with Rudi's initiation into Wicca.