HistoryData
Historical ConflictBougainville Island

Battle of Slater's Knoll

Australian forces repulsed a major Japanese counterattack on Bougainville Island in April 1945, killing 620 Japanese at a cost of 189 Australian casualties.

Duration & Scope

1945 ongoing

< 1 year

Estimated Total Casualties

2K

Key Facts

Duration
28 March – 6 April 1945 (10 days)
Japanese killed
620
Japanese wounded (est.)
~1,000
Australian casualties
189
Japanese attacking force
~3,300 from the 6th Division
Final assault repulsed by
129 men of 'B' Coy, 25th Infantry Battalion

Strategic Narrative Overview

Beginning in late March 1945, Japanese forces conducted probing raids before escalating to heavy assaults against Australian positions at Slater's Knoll. The defending 7th Brigade, primarily the 25th Infantry Battalion supported by the 9th and 61st Infantry Battalions, employed armour and artillery to blunt each attack. The climactic assault came on the night of 4–5 April, when approximately 1,100 Japanese attacked the knoll and were repulsed by just 129 Australians, with 292 Japanese killed in that single engagement.

01 / The Origins

In 1945, Allied forces were pushing south along Bougainville Island toward Buin as part of the broader Bougainville campaign. The Japanese 6th Division, determined to halt the Australian advance, assembled a force of approximately 3,300 troops including artillery and supporting elements. Wet weather had temporarily stalled the Australian offensive, providing the Japanese an opportunity to mount a concentrated counterattack focused on Slater's Knoll near the Puriata River.

03 / The Outcome

The battle ended in a decisive Australian defensive victory. Japanese forces suffered 620 killed and an estimated 1,000 wounded, while Australian casualties totalled 189. The 7th Brigade's success at Slater's Knoll proved to be its final significant action in the campaign; it was shortly afterwards relieved by the 15th Brigade. The failed Japanese counterattack effectively exhausted their offensive capacity in this sector of Bougainville.

Belligerents & Mobilization Analysis

Side A

1 belligerent

Japan (6th Division)
Peak Mobilized Forces~3K
Estimated Casualties~2K
Casualty Rate49.1%
Forces vs Casualties ratio
0CasualtiesMobilized

Side B

1 belligerent

Australia (7th Brigade)
Estimated Casualties189
Total Casualties (all sides)
1,809
Outcome
Australian defensive victory; 620 Japanese killed, ~1,000 wounded; 7th Brigade subsequently relieved by 15th Brigade

Kinetic Engagement Axis

Major engagements timeline (1945–present)Timeline of major military engagements plotted chronologically.1945present1945Final assault on…Side B

Scroll horizontally to view full axis. Events plotted relatively.

Side A victorySide B victoryInconclusiveDecisive / turning point

Location

Map of Papua New GuineaMap of Papua New GuineaPapua New Guinea