On 2nd June 1917, the steamer, while on a voyage from Auckland to San Francisco with a cargo valued at £1,250,000, and consisting of tallow, flax, gum, hides, pelts and 42 live sheep, was passing Raoul when a steamer at anchor was sighted six miles off. As there was no inhabitants on Raoul at the time her situation was peculiar, but the Wairuna had actually passed her, and the suspicions of the master were somewhat allayed, when suddenly a seaplane rose, made for the Wairuna, circled above her, and dropped a weighted canvas bad on the forecastle-head. This bag contained a note calling upon the steamer to steer towards the German cruiser and not to use the wireless or the seaplane would bomb her.
In earnest of her ability to do this, the seaplane dropped a powerful bomb 20 metres ahead of the steamer, after which she flew over the middle of the ship just above the funnel. As the Wairuna was apparently within range of the guns of the other vessel, which was now under way, the master considered that no action of his would affect the final capture of his ship. To carry on would cause a useless sacrifice of life, so he obeyed the instructions, and headed his vessel for the other steamer, putting the engines at 'slow' in order to have time to throw overboard code books, papers etc, before being boarded.
The vessel turned out to be the German commerce raider SMS Wolf, a large steamer with a speed of 10 knots and a crew of 400. She was heavily armed.
A boarding party was put on board the Wairuna and the provisions and coal were transferred to the Wolf, this taking two weeks due to delays because of bad weather. Once everything of use was removed the Wairuna was sunk by a combination of bombs and then gunfire on the 17th June..
The Wairuna was 3947 tons gross and 2530 tons net, built at Newcastle-on-Tyne in 1904 by Sir W G Armstrong, Whitworth and Company. Length 360ft, beam 47.4ft, depth 26.7ft. The Wairuna was owned by the Union Steam Ship Company and commanded by Captain H C Saunders.