 Complete the following phrase:  When the First World War broke out, Burston was without a military role but was called up for active duty despite being 58 years of age. He initially served several months on the Home Front as the chairman of the Officers Selection Committee. In April 1915, he was enlisted in the Australian Imperial Force as a colonel and appointed commander of the 7th Brigade, which included the 25th to 28th Battalions. He departed Australia with the brigade in June and all elements had arrived in Egypt by early August. The next month, he was promoted to temporary brigadier general. In September, he led the brigade to Gallipoli to participate in the 