From ErfWiki

Proposed Canon

Site of the battle in which Lord Manpower the Temporary was croaked.^Erf-b1-p002

When the decrypted Ansom marches on Warchalking after TBfGK, it is a small level 2 city held by Unaroyal and described as being valuable primarily for its farms. It also possesses an orchard and a mill. Its defenses consist of its location on a small hill, an earthen berm capped with stones for an outer wall featuring an iron gate between stone blockhouses, and an inner garrison fortress of logs around a stone tower with a wooden roof.

Speculation

The side that won the battle vs. Lord Manpower and conquered Warchalking might have been Unaroyal, because they held that city when it was reconquered by Gobwin Knob.

Real World Reference

Warchalking is the drawing of symbols in public places to advertise an open Wi-Fi wireless network.