legionary fortress at the mouth of Strath Tay, guarding the main roads to Inverness Inverquharity (near Kirriemuir) a fortlet-sized station at the east end of Glen Clova Cardean, Stracathro and Doune are sited further away from their respective traffic corridors, although fulfilling the same function. Role It has traditionally been thought that these forts were meant to prevent invasions out of the Scottish Highlands into Roman-held territory. This may have been the intention, in cooperation with the other forts on the Gask Ridge and along Strathmore, as only the legionary fortress of Inchtuthil with 5,000–6,000 soldiers would have been strong enough to deal with a major incursion. The smaller forts were more likely to serve as a disincentive to small-scale raiding parties. The relationship between the Glenblocker forts and the Gask Ridge has in the past been seen as a staged withdrawal. Recent research suggests that the three elements are part of the same frontier system, stretching roughly from Loch Lomond to Montrose. In this hypothesis, the Glenblocker forts controlled access to valleys in the frontier area, which loop back into the frontier, rather than link with the Iron Age settlements further north. Their value as a block to invasion is doubtful, as their situation would have allowed supervision but they lacked the manpower to deter anything but cattle rustling. Only the legionary fortress at Inchtuthil, conveniently situated for access into Braemar and its hinterland, is large enough to have functioned as a defensive fortification or a jumping-off point for an invasion. The Gask Road and the towers alongside it in this hypothesis guarded the strategically important link to the harbours at the Firths of Tay and Forth and the southern part of the province. Tacitus writes in De vita Iulii Agricolae that Agricola was fighting in the area in around 80 AD; the latest coinage dates from 86 AD. This would suggest that the forts were occupied for six years at most. Recent archaeology has shown that many of the forts on the Gask Ridge were rebuilt, sometimes twice, without evidence of destruction through warfare. Further digs may cast some light on this apparent contradiction. The forts of Ardoch, Strageath and Bertha on the Gask Road, as well as the forts of Cargill in Strathmore and the glenblocker fort of Dalginross have also produced Antonine material attesting to a reuse of the sites contemporary with the Antonine Wall. In