 Complete the following phrase:  The 21st Field Regiment was an Australian Army artillery regiment raised as part of the all volunteer Second Australian Imperial Force during World War II. Formed in October 1939, the regiment was assigned to the 6th Division. Shortly after it was raised, the regiment was deployed to the Middle East, where it was briefly re-roled as an anti-aircraft regiment before returning to the field artillery role. In 1941, the regiment served in North Africa and in Greece, before being withdrawn back to Australian in early 1942, following Japans entry into the war. In late 1942, and early 1943, the regiment took part in the defence of Port Moresby during the fighting along the Kokoda Track, before taking part in the Battle of BunaGona and the 