The 6th contingent sailed from New Zealand on 30th January 1901. Throughout their war service they and the 5th Queensland Bushmen operated under General Plumer in almost every part of the seat of war, and the column distinguished itself by consistently good work. They could not have been more fortunate in their column commander. In the despatch of 8th May 1901 Lord Kitchener narrated the work of numerous columns in the North-eastern Transvaal in April, and said that he brought Plumer's troops from the Orange River Colony to Pretoria, and directed him to occupy Pietersburg in the north of the Transvaal, a district which, up to that time, had not been visited by British troops. General Plumer left Pretoria on 26th March and occupied Pietersburg on the morning of 8th April. During the advance 48 Boers were captured or surrendered. In Pietersburg other 46 Burghers surrendered; and the force took 1 gun and an immense quantity of ammunition. Between 14th and 28th April the results included 91 prisoners, 20 surrenders, 1 maxim, and more ammunition. On 24th April Captain Markham of the 6th was able to assist Lieutenant Reid of the 4th Imperial Bushmen in bringing off a fine capture. Correspondents about this time frequently referred to Captain Markham's good work. Plumer was now directed to march south to Eerste Fabriken, and he arrived there on 4th May. On the 14th the column again set out as one of several instructed to co-operate in clearing the country between the Delagoa and Natal railways. At Kromdrai, on 16th May, there was some stiff fighting, and on the 25th May a convoy was most severely attacked near Bethel, when some Colonials greatly distinguished themselves. Plumer arrived at Standerton at the end of May, and on 1st June started on another trek, this time to the extreme east of the Transvaal, making his way into the wild country, mountains, and almost impenetrable bush on the boundaries of Zululand and Swaziland. On this expedition many prisoners and horses were taken, but not without losses on the British side. Lieutenant F J Ryan was killed on 6th June, and there were other casualties in both corps about this time. On 28th June Plumer left Utrecht and marched north to Lake Chrissie, where he arrived on 7th July. In the despatch of 8th August, para 5, Lord Kitchener noted that Plumer's column was in the second week of July taken by rail to Bloemfontein, whence on the 23rd they marched west to Modder River, almost on the tracks of Lord Roberts' army when he first invaded the Orange Free State, the direction being reversed. On this march some prisoners and stock were captured. On 4th August Plumer's men again moved out to take part in driving operations in the south-west of the Orange River Colony. On the 11th he returned with 32 prisoners and many cattle, and between the 15th and 30th he operated between the Modder and Orange Rivers, making more captures. He reached the Bloemfontein railway on 30th August and moved into the south-east of the Colony: here some very hard fighting and no little pursuing was done, the enemy being frequently found in strength. On 22nd September 1901 "a party of New Zealanders under Major Tucker (of the 6th contingent), belonging to Lieutenant Colonel Colvin's column (one of those under Plumer's direction), was engaged on the Elandsberg with 150 Boers under Field-Cornets Hugo and Bothnia, both of whom, with several other prisoners, were captured". On 27th September there was stiff fighting at a drift on the Caledon, in which the Queenslanders suffered most of the casualties. The despatch of 8th October further narrated that in conjunction with operations south of Thabanchu "General Plumer despatched 200 New Zealanders under Major Andrew (of the Indian Staff Corps, attached 6th contingent) from Wepener to hold Mokari Drift on the Caledon. This party reached the drift on the 27th September, just in time to anticipate some 300 to 400 Boers who were about to cross the river to the south-east. In some sharp fighting which followed, the enemy, who were driven westward, left 6 dead and 7 wounded on the field".
In consequence of the enemy's activity in the south of the Transvaal, and the threatened reinvasion of Natal, Plumer's troops were, early in October 1901, railed to Volksrust, on the northern border of Natal. They marched from that station towards Wakkerstroom, and in that district they operated for several months.
In the despatch of 8th January 1902 Lord Kitchener dealt with the work of General Plumer's troops in the Eastern Transvaal, and said that "while watching the hilly district to the north of Wakkerstroom on 3rd January, a party of General Plumer's New Zealanders became hotly engaged with the enemy in the vicinity of Twyfelaar, when, despite the loss of the officer in command, who was wounded, and 20 (?) of their numbers, they effected the capture of 300 cattle and a waggon-load of ammunition". The casualties reported on the 3rd were Sergeant Major Smith killed, Lieutenant Mitchell and Sergeant Major Lewin and two men wounded.
"Another severe encounter between the Boers and General Plumer's troops took place on the following day (at Onverwachte), when about 50 of our mounted troops, under Major Vallentin, who were following up the commando which had been engaged with the New Zealanders, were suddenly attacked by several hundreds of the enemy. The Boers advanced at a gallop, with about 100 men in first line, and about 50 thrown back on each flank. The whole movement was covered by heavy fire from several hundred dismounted riflemen in the background; severe hand-to-hand fighting ensued, in which, I regret to say, Major Vallentin and 18 of his men were killed, and 5 officers and 28 men wounded, before the arrival of reinforcements, under Colonel Pultney, compelled the enemy to retire. The Boers, who were led on this occasion by General C Botha on the one flank, and General J D Opperman on the other, fell back northwards, leaving 9 dead and 3 wounded in our hands. Amongst the former was General Opperman, who held chief command over a group of commandos, as well as the personal leadership of the Swaziland Commando".
Onverwachte was one of the most severely fought engagements of the second phase of the war. A member of the 19th company Imperial Yeomanry, who was present, said that they had been following up Boers all forenoon, and had halted, dismounted, and were at their midday meal, when they were surprised by the enemy, who had gathered behind a rise not far away. The chief losers were: the Hampshire Mounted Infantry, 7 killed and 5 wounded; 19th company Imperial Yeomanry, 1 officer and 1 man killed, 8 wounded; 5th Queensland Bushmen, 12 men killed, 2 officers and 20 men wounded.
The column continued for some time to work in the Eastern Transvaal, and on several occasions made substantial captures.