History Background thumb|The extent of Mercia during the Mercian Supremacy, showing the line of Offa's Dyke (red) thumb|right|Wat's Dyke in brown; Offa's Dyke in red thumb|Schematic cross-section of Offa's Dyke, showing the design intended to protect Mercia against attacks/raids from Powys.
History Background thumb|The extent of Mercia during the Mercian Supremacy showing the line of Offa's Dyke (red) thumb|right|Wat's Dyke in brown; Offa's Dyke in red thumb|Schematic cross-section of Offa's Dyke showing the design intended to protect Mercia against attacks/raids from Powys