Analyses of skeletal injuries dating from the Archaic period show that Northwest coast nations, particularly in the North where most Haida communities were situated, engaged in battles of some sort, though the number of battles is unknown. The presence of defensive fortifications dating from the Middle Pacific period show that the incidence of battles rose somewhere between 1800 BC and AD 500. These fortifications continued to be in use during the 18th century as evidenced by Captain James Cook’s discovery of one such hilltop fortification in a Haida village. Numerous other sightings of such fortifications were recorded by other European explorers during this century.