On 18 January 1885 the Chinese cruisers Nan Chen, Nanrui (南瑞) and Kaiji (開濟) left Shanghai, accompanied by the frigate Yuyuen and the composite sloop Chengqing (澄慶), and sailed towards Formosa.

According to L. C. Arlington, an American naval officer serving as a 'foreign adviser' aboard the frigate Yuyuen, the sortie was made in a mood of deep despondency.

The French, weary of the monotonous routine of the blockade and frustrated with their inability to get to grips with the Chinese, jumped at the chance of destroying half the Nanyang Fleet at sea.

Courbet sailed north from Keelung in early February to hunt down the Chinese with the ironclads Bayard and Triomphante, the cruisers Nielly, Éclaireur and Duguay-Trouin, the gunboat Aspic and the troopship Saône.

[2] On 9 February, with supplies of coal beginning to run short on some ships, Courbet was obliged to send the cruiser Duguay-Trouin back to Keelung.

Courbet immediately headed southwards, and led the squadron at night through the hazardous passages of the Chusan Islands to close with the enemy as soon as possible.

The bay was also full of junks and sampans which had taken refuge there from the French, and Duboc and Gourdon hoped that their small launches, painted black for camouflage, could mingle with these vessels and approach their targets unseen.

He was aboard Yuyuen when the frigate was attacked by the two French launches, and described vividly the panic that ensued after the explosion of the spar torpedoes, as the Chinese crewmen abandoned ship and swam for the shore.

The Chinese artillery fire was wildly inaccurate and at least one shell seems to have hit the composite sloop Chengqing, crippling her also: The scene that now occurred almost beggars description.

The fault rested entirely with the Chinese—even at the last moment, had they made any attempt to repel the torpedo boat they might have warded off the catastrophe, and possibly sunk the enemy instead.

Gourdon and Duboc were feted on their return to the French squadron, and were both decorated for the heroism they had shown in pressing home their torpedo attack under fire.

Embarrassed by the loss of one of their ships to friendly fire, the Chinese authorities later claimed that Chengqing had been deliberately scuttled to prevent her from falling into the hands of the French.