By November 1941 Helena had received 1.1-inch anti-aircraft guns, while removed .50-calibre weapons were retained on wheeled mounts for flexible firing positions. Japanese aircrews expected to find the battleship Pennsylvania in her usual berth. Instead, the overlapping profiles of the minelayer Oglala and cruiser Helena created a false battleship silhouette. A torpedo passed beneath Oglala and exploded against Helena, flooding machinery spaces and severing wiring to the main and secondary guns. Helena restored gun power with a forward diesel generator, while the same blast loosened Oglala's plates and contributed to the minelayer's capsizing.
Notable Point · 1:18:00-1:21:15
Helena is mistaken for a battleship at Pearl Harbor
A Japanese torpedo aimed at a silhouette mistaken for Pennsylvania passed beneath Oglala and exploded against Helena, flooding machinery spaces and cutting gun power.