Shoushan Cave Fortification Complex

高雄寿山洞窟陣地群

Entrance to Gushan Cave (鼓山洞), a 1939 Japanese-era air-raid tunnel on Shoushan mountain, Kaohsiung — 鼓山洞入口——壽山洞窟陣地群中已開放觀光的日治防空隧道 — Sin-siōng, CC BY-SA 4.0

An extensive network of Japanese military tunnels, cave fortifications, and underground positions excavated into Shoushan (Monkey Mountain) in Kaohsiung during WWII. As the headquarters of the Kaohsiung Fortress (高雄要塞), the mountain was honeycombed with dozens of tunnel systems serving as coastal defense gun emplacements, ammunition magazines, command posts, communications centers, and air-raid shelters. Distinct from the individual Gushan Cave tourist site, this complex encompasses the broader network of military cave positions spread across Shoushan that formed the core of Japan's southwestern Taiwan defense system.

Prefecture

Kaohsiung

City

Gushan

Region

Taiwan

Significance

Major

Today

Memorial Site

Access

Restricted

Location accuracy

Approximate

Period

1937–1945

Images

Interior of Gushan Cave tunnel showing the excavated rock passage of the Japanese military air-raid shelter — 鼓山洞坑道內部——日軍開鑿的防空隧道岩壁通道 — Sin-siōng, CC BY-SA 4.0

Deep inside the Gushan Cave tunnel complex, showing stalactite formations on the ceiling of the Japanese-era military shelter — 鼓山洞坑道深處——天花板上的鐘乳石見證數十年地下水滲透 — Sin-siōng, CC BY-SA 4.0

Tunnel junction inside Gushan Cave showing the branching passages of the Japanese military underground shelter network — 鼓山洞坑道分岔處——展示日軍地下防空壕的「丹」字形通道結構 — Sin-siōng, CC BY-SA 4.0

Illuminated section of Gushan Cave tunnel, part of the Shoushan cave fortification network now open as a heritage site — 鼓山洞照明坑道段——壽山洞窟陣地群中現作為文化資產開放的部分 — Sin-siōng, CC BY-SA 4.0

History

The Shoushan Cave Fortification Complex comprises the extensive network of military tunnels, underground bunkers, and cave defensive positions that the Imperial Japanese Army excavated throughout Shoushan mountain in Gushan District, Kaohsiung. This mountain, rising 356 meters above the entrance to Kaohsiung Harbor, was transformed into one of the most heavily fortified underground military complexes in colonial Taiwan.

Establishment of the Kaohsiung Fortress

The strategic importance of Shoushan was recognized early in the Japanese colonial period. In August 1937, following the outbreak of the Second Sino-Japanese War, the Imperial Japanese Army formally established the Kaohsiung Fortress Headquarters (高雄要塞司令部), at first in the Qianjin area of the city and from December 1937 at Kotobuki-chō (壽町) at the foot of Shoushan. Initially classified as a third-class fortress, it was upgraded to second-class in August 1939 and first-class by December 1942, reflecting the growing strategic importance of Kaohsiung as Japan's southernmost major port and naval logistics base.

Construction of the Cave Fortification Network

The tunnel and cave fortification network was developed in phases. Early construction in the late 1930s focused on air-raid shelters for military and industrial personnel — including the well-known Gushan Cave (鼓山洞), a large air-raid tunnel built by the Railway Department to shelter its staff and passengers. However, from November 1943 onward, the fortification program was dramatically expanded as Japan shifted from offensive to defensive strategy. The original sea-oriented defense plan was transformed into a land-and-air focused defensive posture, with Shoushan designated as the central strongpoint for anti-landing operations along Taiwan's southwestern coast.

The fortification network included diverse installations: coastal defense gun positions (including 28cm howitzers and 15cm guns), anti-aircraft artillery emplacements, machine gun bunkers at mountain road entrances, underground command centers with independent water and power systems, ammunition storage caves, communications facilities, and extensive personnel shelters. The Xiziwan Tunnel, originally excavated in 1927-1928, was expanded to serve as a local command center with ventilation, water supply, shower facilities, and living quarters.

Final Defensive Preparations (1945)

In February 1945, with intelligence indicating a potential American landing at Kaohsiung following the fall of Luzon, the Kaohsiung Fortress garrison was reorganized as the Independent Mixed 100th Brigade, with the fortress commander becoming brigade commander in March. Between February and August 1945, construction of defensive positions on Shoushan reached fever pitch. Machine gun bunkers were built at every mountain road entrance, and the tunnel network was expanded to accommodate the brigade's personnel. The city government counts more than 200 military tunnels across Kaohsiung, many of them on Shoushan. The North Caishan Tunnel Artillery Bunker, reportedly armed with a 127mm coastal defense gun, was positioned to defend the coastline from Zuoying Naval Harbor to Tainan.

Postwar and Present Day

After Japan's surrender in August 1945, the cave fortification complex was taken over by ROC military forces. During the martial law era, some tunnels — including Gushan Cave — were repurposed by the Taiwan Garrison Command for security purposes, reportedly including interrogation rooms. The mountain remained under strict military control for decades. Beginning in the 2000s, as military restrictions were gradually relaxed, individual tunnel sites began to be opened to the public. Gushan Cave was formally opened as a military-heritage tourism site in May 2019. However, the vast majority of the tunnel network remains unexplored by the public, with many entrances sealed or hidden in the dense vegetation of Shoushan National Nature Park (established 2011). The complex stands as one of the most significant surviving examples of Japanese WWII underground fortification architecture in Taiwan.