By the end of March the New Zealand Division was concentrated in Macedonia. The 5th Brigade Group had arrived from England, thus the three contingents were together for the first time in the history of the Division. Their first role was preparing a defensive position, in conjunction with the Greeks, from the coast south of the River Aliakmon to Veria Pass. The long front was too vulnerable for the forces available and, following the enemy's attack on Yugoslavia and Greece on 6 April, the Division was ordered to retire to a strong position on the line of the Passes, the 4th Brigade Group to Servia, the 5th and 6th Brigade Groups to Olympus. A quick withdrawal was made in rain and snow. This was accomplished without loss of equipment or supplies, the troops showing a high standard of discipline and endurance in their first trial. Rain and overcast skies were a blessing, as no enemy aircraft molested our forces. This retirement was completed by 10 April.

On the 12th the Australians and New Zealanders were formed into the 2nd Anzac Corps, giving great satisfaction. From the 10th the Division fought several actions mainly as three separate brigade groups, each comprising all arms. The Machine Gun Battalion detachment on the Yugoslav frontier fired the first New Zealand shots at Veve at 9 p.m. on 10 April. On the 13th the Divisional Cavalry and Artillery on the Aliakmon River fought delaying actions, retiring over Olympus Pass on the 14th. The 4th and 5th Brigade Groups under Brigadiers Puttick and Hargest² respectively came into action simultaneously at the historic Servia and Olympus Passes. The 4th Brigade Group held Servia Pass while Imperial and Greek troops from the Florina Gap withdrew. The infantry action was severe and the Germans suffered heavy casualties. The 5th Brigade page 17 Group, plus the Maoris, were holding the long line of the Olympus position, and the 21st Battalion held the coastal defile and railway tunnel near Platamon. At Olympus the Artillery, firing a phenomenal number of rounds, smashed the German tank advance, the infantry beating off heavy attacks made through the woods under cover of mist. The success of the German thrust against the Greeks on the left threatened the rear of the Olympus position and a withdrawal to the Thermopylae line was ordered for 16 and 17 April, Brigadier Barrowclough's¹ 6th Brigade Group moving to a covering position south of Elasson. After fighting with great determination and repulsing heavy attacks, the 4th and 5th Brigade Groups and the Australians retired again under the cover of mists to the south of the 6th Brigade Group. Meanwhile, the 21st Battalion had been forced back from the tunnel by tremendous odds, including a large armoured force. Later, with Brigadier Allen's² Australian Brigade Group, they held the Peneios Gorge position. The 21st Battalion suffered heavy casualties. The stands at Peneios and Elasson, where British, Australian, and New Zealand artillery took toll of enemy tanks, breaking their attacks, were vital.