Khmer Frontiers and Fortifications

Khmer political reach in mainland Southeast Asia shifted across the Angkorian centuries, from the ninth to the fifteenth century. Rulers fought neighboring kingdoms and used roads to move between cities, but these routes often linked settlements that were already active before Angkorian kings built shrines or bridges along them. At Angkor, in present-day Cambodia, walls and gates regulated entry to the capital; at Angkor Wat, an outer wall first enclosed a temple and was later adapted for defense.

Campaigns and roads across the region

Champa was a neighboring kingdom along the coast of what is now central Vietnam. In 1145, the Khmer ruler Suryavarman II captured its city of Vijaya. Cham forces later regained Vijaya. Jayavarman VII subsequently led campaigns into Champa and Khmer forces occupied territory there during the early thirteenth century. The Khmer withdrawal around 1220 ended that phase of control. Khmer control of Vijaya was temporary, while the Angkor–Phimai road network continued to connect settlements across the region.

Roads helped connect Angkor with regional centers. The route northwest to Phimai crossed the Khorat Plateau in present-day northeastern Thailand, while other corridors ran toward Koh Ker and the Mekong valley. Archaeologist Mitch Hendrickson notes that surveys found twenty-three prehistoric sites along the Angkor–Phimai route. These communities and earlier travel paths preceded the Angkorian road monuments, so later rulers improved and marked corridors that already joined populated places.

A 1191 inscription from Preah Khan lists 121 fire shrines, small roadside religious buildings, along three routes between Angkor and regional cities. Seventeen are associated with the Phimai road. Archaeologists identify a sequence of small temples built from laterite, an iron-rich stone cut into building blocks, along this route with those stops. Raised earth roads, laterite bridges and nearby water tanks helped travelers cross wet ground and find water along the way. These roadside foundations added religious buildings and stopping places to routes that already connected established communities.

Gates at the capital

Jayavarman VII developed Angkor Thom, the walled capital at Angkor, in the late twelfth and early thirteenth centuries. Roads led through its monumental gates toward the central temple of Bayon. A moat and wall enclosed the city, concentrating movement at a small number of entrances. The moat also belonged to Angkor’s managed water landscape.

Zhou Daguan, a Chinese visitor who stayed at Angkor in 1296–1297, described a wall with five gates, a broad moat and raised causeways leading over it. He noted stone figures gripping a serpent-shaped bridge rail and guards who closed the gates at night and opened them in the morning. The schedule made the gates a working checkpoint: entry into the capital passed through guarded openings and depended on when they were open.

A temple wall adapted for defense

Angkor Wat offers a different history of enclosure. Its large outer wall was built in the early twelfth century as part of the temple’s original precinct, not as the outer wall of Angkor Thom. It encloses an area over 800 metres by 1,000 metres. Laterite forms most of the wall, while sandstone marks the entrance pavilions.

Archaeologist David Brotherson mapped thousands of holes and notches cut into this wall. Horizontal holes on its inner face, about three to four metres above ground, align with slots along the top. He argues that the horizontal holes held wooden platforms inside the wall, giving defenders higher ground above attackers, while slots along the top supported a timber barrier that obstructed entry. The alteration followed the original temple construction, but no direct date survives for these works; Brotherson places them broadly between the late thirteenth and early seventeenth centuries. This period included Angkor’s loss of political centrality and the expansion of Ayutthaya, a kingdom centered in present-day Thailand.