 Complete the following phrase:  The 3rd Light Horse Brigade was a mounted infantry brigade of the Australian Imperial Force AIF, which served in the Middle Eastern theatre of World War I. The brigade was initially formed as a part-time militia formation in the early 1900s in Victoria. In 1914, the brigade was re-constituted as part of the AIF. The brigade first saw action while serving with the Australian and New Zealand Army Corps during the Gallipoli campaign where they were noted for their attack during the 