 After participating in the occupation of German Samoa, Eastwood left New Zealand with the Third Reinforcement in February 1915, arriving at Suez by sea forty days later.In April 1915, his battalion was deployed to Gallipoli, where he was awarded the Military Cross (MC) for his leadership of a column during a night assault on 6–7 August 1915.After service with the Egyptian Expeditionary Force (EEF), Eastwood's brigade was transferred to France, where in October 1917 he became a general staff officer with the rank of major.