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Battle of Alligator Creek…or Tenaru River? Or was it Ilu?

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The marines nicknamed it Alligator Creek, although the alligators were actually crocodiles. Its official name remains the Battle of the Tenaru River. In reality, though, this first Japanese ground offensive of the Guadalcanal campaign was fought on the shores of the Ilu River. US intelligence had confused the two rivers on the maps the marines were using, and the misnomer stuck.

Although the misnomer was an American mistake, the Japanese would make much more costly errors that resulted in devastating losses for the Ichiki Detachment, named after its respected and battle tested commander, Col. Kiyonao Ichiki. His 28th Regiment had been in the waters off Midway, awaiting the go-ahead to assault the beach, take the island, and then remain as garrison. But the Battle of Midway, as we now know, didn’t quite go the way the Japanese had planned. Ichiki’s 28th Regiment was dropped at Guam, and later moved to Truk. It was from there that Ichiki and 900 of his men headed to Guadalcanal with the mission of retaking Henderson Field, and ultimately kicking marine forces off the island.

The Japanese detachment arrived on Guadalcanal on 19 August. Unbeknownst to the Japanese who saw no sign of the Americans on the island, the marines knew the enemy had landed and were prepared for a fight. Japanese reconnaissance suggested that the bulk of the Allied invasion force had been removed from the island, but in reality the marines were dug in and well hidden to both planes above and troops ashore. This was Japan’s largest error; their intelligence suggested the presence of around 2,000 marines when in reality there were nearly ten times that number. This grave miscalculation fed Ichiki’s arrogance and although a few thousand more Japanese troops were set to arrive within a few days to complement his miniscule force, Ichiki was confident his 900 could easily defeat the 2,000 marines he believed to be on the island. In addition, the Japanese had no respect for the American fighter, who was new to warfare where they had been fighting for nearly five years. And although intelligence had also discouraged Ichiki against frontal assaults, that was exactly what he decided to do.

On this day 70 years ago, the Japanese attempted and failed to retake Henderson Field in what is remembered as the Battle of the Tenaru River. The Americans had the upper hand for two reasons. First, they had ambushed a Japanese patrol, taking down several officers who carried maps illustrating where the marine line was weak. Those areas were reinforced. Second, the now legendary Jacob Vouza, a native Solomon Islander, evaded death to warn the marines of what was coming. He had been captured by the Japanese while patrolling, tied up, tortured for information, bayoneted several times including in his throat and stomach when he refused to speak, and was assumed dead. But he wasn’t. He reportedly chewed himself free and reached US forces in time to warn them that the enemy would be there momentarily.

The Ichiki Detachment arrived shortly after midnight on 21 August, and came over a sandbar in the river in droves, making an easy target for the dug-in marines with their Browning .30 calibers and 37 mm anti-tank guns firing canister rounds, essentially enormous shotgun shells that sprayed projectiles over a wide field. The Americans lost 43 men in the Battle for Alligator Creek, but the long held image of the immortal, invincible Japanese soldier was gone. American morale was given a much-needed boost, while the Japanese were handed a massive blow. Nearly 90% of the Ichiki Detachment—800 of a little over 900 troops—was wiped out by marines who knew they were coming.


To learn more about the Guadalcanal Campaign, its heroes, and the weapons used to win victory see our Focus On: Guadalcanal.


This post by Curator Meg Roussel

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