ASL Map Spotlight: Edson’s Ridge

Edson's Ridge was a pivotal battle during the invasion of Guadalcanal, 1942.

/ 1827 Words ~ 8.1 Minutes

ASL Map Spotlight: Edson's Ridge
Operation Watchtower

The Battle of Edson’s Ridge, also known as the Battle of the Bloody Ridge, Battle of Raiders Ridge, and Battle of the Ridge, was a land battle of the Pacific campaign of World War II between Imperial Japanese Army and Allied (mainly United States Marine Corps) ground forces. As part of overall Operation Watchtower, the battle took place from 12–14 September 1942, on Guadalcanal in the Solomon Islands, and was the second of three separate major Japanese ground offensives during the Guadalcanal campaign.

In the battle, U.S. Marines, under the overall command of U.S. Major General Alexander Vandegrift, repulsed an attack by the Japanese 35th Infantry Brigade, under the command of Japanese Major General Kiyotake Kawaguchi. The Marines were defending the Lunga perimeter that guarded Henderson Field on Guadalcanal, which was captured from the Japanese by the Allies in landings on Guadalcanal on 7 August 1942. Kawaguchi’s unit was sent to Guadalcanal in response to the Allied landings with the mission of recapturing the airfield and driving the Allied forces from the island.

Edson’s Ridge Map

This map and action can be found in Multi-Man Publishing’s Advanced Squad Leader historical study module: Operation Watchtower. This module is, unfortunately, out of print but can be found on the used market.

ASL Map Spotlight: Edson's Ridge
Edson’s Ridge Map, Guadalcanal, North is to the right

The Battle of Edson’s Ridge

The Battle of Edson’s Ridge was a crucial engagement between the Japanese and the Allied forces on Guadalcanal during World War II. It took place from September 12 to 14, 1942, and involved a series of fierce nighttime attacks by the Japanese 35th Infantry Brigade against the U.S. Marines defending a strategic ridge south of Henderson Field, the airfield that the Allies had captured from the Japanese in August. The battle was named after Lieutenant Colonel Merritt A. Edson, the commander of the 1st Raider Battalion, who played a key role in organizing the defense of the ridge. The battle was also known as the Battle of the Bloody Ridge, the Battle of Raiders Ridge, and the Battle of the Ridge.

The battle was part of the Guadalcanal campaign, which began on August 7, 1942, when the Allies launched an amphibious invasion of the island, which was occupied by the Japanese since May. The main objective of the invasion was to seize Henderson Field, which was under construction by the Japanese and could be used as a base for air operations in the Solomon Islands. The Allies succeeded in capturing the airfield, but faced constant attacks from the Japanese naval, air, and ground forces, who were determined to recapture it and drive the Allies from the island.

ASL Map Spotlight: Operation Watchtower - Edson's Ridge
Edson’s Ridge Planning Map
ASL Map Spotlight: Operation Watchtower - Edson's Ridge
Edson’s Ridge, First Phase

The Japanese high command realized that the loss of Guadalcanal could have serious consequences for the outcome of the war in the Pacific, and decided to send reinforcements to the island. One of these reinforcements was the 35th Infantry Brigade, commanded by Major General Kiyotake Kawaguchi, which arrived at the island on September 4. Kawaguchi’s brigade consisted of about 6,000 men, including three infantry battalions, an artillery battalion, and a tank company. Kawaguchi’s mission was to launch a surprise attack on Henderson Field and destroy the Allied aircraft and facilities there.

Kawaguchi planned to attack the airfield from two directions: the main attack would come from the south, along Lunga Ridge, which was a narrow, grassy, and wooded hill that overlooked the airfield; the secondary attack would come from the east, along the Matanikau River, which was a natural obstacle that separated the Japanese and Allied positions. Kawaguchi hoped to coordinate his attack with a naval bombardment and a diversionary attack by another Japanese unit, the Ichiki Detachment, which had landed on the island earlier.

ASL Map Spotlight: Operation Watchtower - Edson's Ridge
U.S. Marines resting on Guadalcanal

However, Kawaguchi’s plan faced several difficulties. First, he underestimated the strength of the Allied forces on the island, which numbered about 12,000 men, mostly U.S. Marines, under the command of Major General Alexander Vandegrift. Second, he had poor intelligence and communication with his own troops, as well as with the Japanese navy and air force. Third, he had to deal with the harsh terrain and weather conditions of the island, which slowed down his movement and supply. Fourth, he was unaware that the Allies had detected his presence and movements, thanks to the help of local scouts and coastwatchers, who provided valuable information to the Allied commanders.

The Allies were alerted to the threat of Kawaguchi’s attack by the discovery of a large Japanese supply dump near the village of Tasimboko, east of the Matanikau River, on September 8. A raid by the 1st Raider Battalion and the 2nd Battalion of the 5th Marine Regiment destroyed the dump and captured several documents that revealed Kawaguchi’s plan and strength. Vandegrift decided to reinforce the defenses of Henderson Field, especially along Lunga Ridge, which he correctly identified as the most likely avenue of attack. He assigned the task of defending the ridge to Edson, who had about 840 men under his command, including his own 1st Raider Battalion, the 1st Parachute Battalion, and elements of the 2nd Battalion of the 5th Marine Regiment. Edson deployed his men along a 1,000-yard line that ran across the ridge, with the 1st Raider Battalion on the right, the 1st Parachute Battalion on the left, and a reserve force of about 200 men behind the center. He also had the support of artillery and mortars from the 11th Marine Regiment and the 67th Fighter Squadron, which were based at Henderson Field.

ASL Map Spotlight: Operation Watchtower - Edson's Ridge
Guadalcanal’s Bloody Ridge, September 1942

The battle began on the night of September 12, when the Japanese navy shelled Henderson Field and the surrounding area, followed by a series of air raids. Kawaguchi launched his main attack along Lunga Ridge, with his three infantry battalions advancing in a column formation. The Japanese encountered the Marine outposts on the ridge and engaged them in fierce firefights. The Marines resisted the Japanese assaults, but were gradually pushed back by the sheer weight of numbers and the ferocity of the enemy. The Japanese managed to break through the Marine line at several points, especially on the left flank, where the 1st Parachute Battalion was heavily outnumbered and outflanked. The Japanese also infiltrated the rear of the Marine positions, creating confusion and chaos among the defenders. Edson realized that his line was in danger of collapsing, and ordered a withdrawal to a secondary line, about 500 yards to the north, on a small hill that became known as Hill 123. He also requested reinforcements and more artillery support from Vandegrift.

The Marines regrouped on Hill 123, which was a natural strongpoint that offered a clear view of the surrounding area. Edson organized the defense of the hill, placing his reserve force on the crest, the 1st Raider Battalion on the right slope, and the remnants of the 1st Parachute Battalion on the left slope. He also placed machine guns and mortars on the hill, and coordinated the fire of the artillery and the aircraft. The Japanese continued their attacks throughout the night, but were unable to dislodge the Marines from the hill. The Japanese suffered heavy casualties from the Marine fire, as well as from friendly fire, as their own artillery and air force mistakenly bombed their positions. The Japanese also ran out of ammunition and supplies, and had no communication with their headquarters or other units. Kawaguchi decided to call off the attack and withdraw his troops to the south, leaving behind hundreds of dead and wounded.

ASL Map Spotlight: Operation Watchtower - Edson's Ridge
Dug-in U.S. Marines on Edson’s Ridge

The next day, September 13, the Marines consolidated their positions on Hill 123, and repelled several minor Japanese probes. They also received reinforcements from the 2nd Battalion of the 1st Marine Regiment, which arrived from the west. The Japanese remained in their positions south of the ridge, and prepared for another attack. Kawaguchi hoped to coordinate his attack with the secondary attack from the east, which was led by Colonel Akinosuke Oka, the commander of the 124th Infantry Regiment. Oka’s regiment had crossed the Matanikau River on September 11, and had advanced toward Henderson Field, but had encountered stiff resistance from the Marines on the east bank of the river. Oka had also lost contact with Kawaguchi, and was unaware of the situation on Lunga Ridge.

The final phase of the battle occurred on the night of September 13-14, when Kawaguchi launched his last desperate attack on Hill 123, and Oka launched his delayed attack from the east. Both attacks failed miserably, as the Marines held their ground and inflicted heavy losses on the Japanese. The Japanese were unable to break through the Marine defenses, and were forced to retreat to the south and the east, respectively. The battle was over, and the Marines had won a decisive victory.

ASL Map Spotlight: Operation Watchtower - Edson's Ridge
American Marine stands near positions on Hill 123

The Battle of Edson’s Ridge was a turning point in the Guadalcanal campaign, as it demonstrated the determination and resilience of the Marines, and the futility and wastefulness of the Japanese attacks. The battle also had a significant impact on the morale and confidence of both sides, as the Marines gained a sense of pride and accomplishment, and the Japanese suffered a loss of prestige and initiative. The battle also had strategic implications, as it prevented the Japanese from recapturing Henderson Field, which remained in Allied hands for the rest of the campaign. The airfield was crucial for the Allied air operations in the Solomon Islands, which supported the subsequent Allied offensives in New Guinea and the Central Pacific.

The Battle of Edson’s Ridge was one of the most intense and bloody battles of the Pacific War, and one of the most heroic and memorable episodes in the history of the U.S. Marine Corps. The battle was a testament to the courage and leadership of Edson, who was awarded the Medal of Honor for his actions, and the bravery and sacrifice of his men, who were nicknamed the “Raiders” and the “Red Devils” by the Japanese. The battle was also a tribute to the cooperation and coordination of the Allied forces, who worked together to defend Henderson Field and the island of Guadalcanal. The battle was a major achievement for the Allies, and a severe setback for the Japanese, in the struggle for the control of the Pacific.

GET TO THE CHOPPA…!!! Get To The Choppa...!!!

ASL Map Spotlights are meant to be quick history lessons on available historical Advanced Squad Leader actions. These short articles are meant to highlight both a short history of the battle portrayed for players unfamiliar with the setting, as well as show the ASL map on which it plays out.

© 2023-2024, Neal Ulen. All Rights Reserved. Copyright & Fair Use Notice. is not affiliated with Hasbro, AH Games, Inc., or MMP, Inc. Advanced Squad Leader is a trademark of AH Games, Inc.


  1. I’ve been meaning to put this one on the table for years but i need to do a complete restudy of the pto rules. This is the year! Thnx for the quick history review.

  2. This is what I call a “blood and guts” module. Maybe not as bad as the bloothbath that is BRT, but its definitely a slugfest. It’s been years since I played it, but was a ton of fun. Underappreciated module in my opinion.

    • Red Barricades and BRT are the bloodiest ASL games I’ve ever played. I can’t imagine Watchtower could remotely compare to them. I havent play it so its possible.



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