During an action the British were held up by heavy machine-gun fire which threatened the 16th’s flank. McCarthy decided to attack the nearest post, which he and Sergeant F.J. Robbins, DCM, MM, succeeded in reaching after a dash across fire-racked, open ground. They captured the machine gun and continued to fight down the trench, inflicting heavy casualties and capturing three more machine guns, until contact was made with the 16th Lancashire Fusiliers. McCarthy, during his advance, had killed twenty enemy and captured five machine guns and fifty prisoners. When he jumped into the last trench the surrendering Germans closed in on him from all sides, took his revolver, patted him on the back and then allowed him to lead them back to the Australian lines. He handed over 500 metres of captured trench to the British. This feat was described in the official history as being, next to Jacka’s at Pozieres, perhaps the most effective individual feat in the history of the AIF.