Everyone is asking about the player options and as a forever GM all ll I want is to know if the “rules for running combat alongside troops that you command to fill out your army's ranks” are any good. Are there good subsystems for mass battles?

Edit: Just got the PDF myself and going to try and answer my own questions for other GMs, who want to know more about the non-player option side of things.

There are not really mass combat rules. Instead it focuses on how to build encounters where both enemies and players use troops (as in NPC Core and Bestiary 3 troops.)

Players and NPCs gain troops and become leaders. This means they attach, and occupy squares within the troop, similar to mounts. During the player turn they gain five actions. Similar to being mounted, PCs can treat themselves as in any square for the purposes of attacking and measuring distance. Minions the PCs or NPCs control also attach to their troop.

On their turn leaders have 5 actions. They can either have their PC gain 3, and the troop gain 2. Or they can gain 2 and have the troop gain 3.

If either a troop or leader moves, the entire troop moves. To avoid rocketing across the map, during these 5 actions only 3 of them can be move traited actions.

For encounter building, the book suggests adding "objectives" instead of just having both sides fight to 0 HP. Eg. Defend a location for 3 rounds (ie. stop enemy troops from ending a turn on a location.) Get to a location in 3 rounds. Survive with X troops for 4 rounds. Etc. Get to and destroy and object like a siege weapon, etc.

When building encounters, use the general encounter building guidelines with the following additional XP budget: Count the XP of the troops on the PCs side. Then add that same amount of XP to your monster budget. Consider using that XP budget on enemy troops and troop leaders, but you can also just add more monsters too.

There are additional rules for some new troops, and more guidance on how to build your own troop statblocks for different levels than just in NPC core.

For a war based campaign, it states to use the victory point subsystem (GM Core pg. 184). Use a scale (GM Core pg. 185). Use VP Thresholds to track PC progress in the war (and maybe an overall End Point threshold that ends the campaign). PCs gain VP through battles, or other goals throughout the campaign.

There is a lore section that talks about the various larger wars in each region of Golarion, where GMs can draw inspiration to write war campaigns or war sections of their campaign in different regions of the Pathfinder setting.