From ErfWiki

Proposed Canon

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

Warchalking is a small level 2 city described as being valuable primarily for its farms.

Speculation

The side that won the battle vs. Lord Manpower and conquered Warchalking might have been Unaroyal, because they are currently holding that city.

Real World Reference

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