Short of space, the captain of E4 embarked three German prisoners and supplied the boats with water, biscuits, a compass, and a course to steer, and they returned safely to base.

[6][7] On 23 November 1914, the British battleships Russell and Exmouth bombarded the German-occupied Belgian port of Zeebrugge, which was being used as a base for German submarines.

[9] On the night of 31 May - 1 June 1916 Defender took an active part in the Battle of Jutland, with the First Destroyer Flotilla operating in support of Beatty's battlecruiser force.

Although the shell failed to explode, it knocked out the boiler room, reducing the ship's speed to about 15 knots (28 km/h; 17 mph), forcing her out of formation with the rest of her Flotilla.

I consider the performances of these two destroyers to be gallant in the extreme, and I am recommending Lieutenant-Commander J. C. Tovey of Onslow, and Lieutenant Commander Palmer of Defender, for special recognition...Lieutenant Commander Palmer wrote after the battle that Onslow had signalled Defender with the following message: We all Captain, officers and ship’s company thank you very much for your kind and most efficient assistance and wish you all possible luck and a long leaveDefender was transferred to the 3rd Battle Squadron in 1916.

On 18 June 1918, Defender was operating in the Strait of Otranto with the destroyer HMS Nymphe whe she became a target in a friendly fire incident.

Both destroyers immediately flashed lights, and the submarine chasers ceased fire and went alongside, discovering that their targets had been Defender and Nymphe.