After the relief of Kimberley Kimberley Light Horse and Diamond Fields Horse troops were amalgamated under the title 'Kimberley Mounted Corps'. According to the despatch of 21st May 1900, para 24 and note, the KMC were at this time 600 strong.
The corps, under Lieutenant Colonel Peakman, operated with Lord Methuen in the Boshof district. On 5th April Lord Methuen was successful in surrounding a detachment under Villebois de Marueil. The kopje on which the enemy had taken up a position was, after shell and rifle fire, assaulted with the bayonet. The enemy lost 7 killed, 11 wounded, and 51 unwounded prisoners. In his report of 6th April Lord Methuen spoke in terms of praise of the way the troops worked, and mentioned Lieutenant Colonel Peakman.
The corps continued with Lord Methuen chiefly about Boshof during April, and frequently had skirmishing. At the end of that month they moved west to join Colonel Mahon's column, which was to start from Barkly West on 4th May for the relief of Mafeking. The work of Mahon's column has already been touched on under the Imperial Light Horse. In Major Pollock's account of the relief, he said: "Finally, just to give one more instance of the fine spirit that animated this gallant little force, it should be mentioned that Lieutenant Watson of the Kimberley Mounted Corps, who was on sick leave at Cape Town, heard of the march to Mafeking, hurried back to the front, and having ridden absolutely alone all the way from Barkly West, joined the column on Sunday, just in time for the fight (near Kraaipan), having covered 220 miles in five days. With such officers and men a commander may safely face pretty long odds". In that fight Captain Maxwell of the KMC and 4 men were wounded.
On the 16th May was fought the stiff engagement outside Mafeking. The Boers attacked Mahon's flanks and rear. Speaking of the latter attack, Major Pollock said: "But the brigadier had complete confidence in Lieutenant Colonel Peakman, who had command of the rearguard, and right well did this gallant officer fulfil the trust committed to him. A considerable number of mounted Boers galloping down by the village of Saani gained the bed of the Molopo river, and from there sought to assail the rear-guard, but so accurate was the fire of the party of Kimberley Mounted Corps that the enemy was not only checked, but was also unable to retire until after nightfall. Lieutenant Colonel Peakman was praised by Major Pollock for the cleverness with which he chose the ground, yet the trial, in spite of the excellent cover, was no light one, the Boer shells pitching all over Peakman's position. Captain C P Fisher and several men of the corps were wounded.
Mahon's column marched from Mafeking to Potchefstroom, and there most of the KMC left the column, which continued its march to Krugersdorp. A portion of the KMC operated for a time with Baden-Powell in the Mafeking-Zeerust district (see Lord Roberts' despatch of 14th August 1900, para 33).
In his brief despatch regarding the relief of Mafeking, dated 23rd May 1900, Colonel Mahon mentioned that on 5th May, the day after leaving Barkly West, he detached Captain Rickman with one squadron of the KMC to join Sir Archibald Hunter, who was then driving the enemy from the border near Warrenton, and whose force marched into the Transvaal and was joined by Mahon at Lichtenburg on 6th June.
In July and onwards part of the KMC were employed in the Krugersdorp-Potchefstroom district. On the occasion of a train being derailed near Bank Station about 20 non-commissioned officers and men were captured, and about the same time one man was killed and Lieutenants Drew and Watson and some men were wounded. On 25th July Klerksdorp, where a squadron was stationed, seems to have been surrendered by Captain Lambart without any serious defence being made (see 'The Times' History, vol iv p 362). On 7th August and for some days thereafter a portion of the corps was in contact with De Wet's forces when these broke across the Vaal. At this time a portion of the corps was employed about the Kimberley - Mafeking line, and a squadron was with Lord Erroll in the Western Transvaal in August and September.
In October, November, and December 1900 the Diamond Fields Horse was in the column of Major General Settle which assisted to clear the western portion of the Orange River Colony (see Cape Police). On 28th November the DFH were in a sharp skirmish near Luckhoff.
When it was seen that Hertzog and other leaders were penetrating to the south-west of Cape Colony the corps was put into Colonel Bethune's column, which, in January and February 1901, assisted to drive these commandos out of Cape Colony. In March, April, and May the DFH were in central Cape Colony, where they were frequently in action under Major Berrange and other commanders. On 1st May Lieutenant Matthews was severely wounded near Cradock.
From May 1900 to May 1901 a section of the Diamond Fields Artillery was in the garrison of Boshof which successfully held that town and repelled many attacks. The main portion of the garrison was the 4th Scottish Rifles (Militia), and a good account of their work is to be found in Colonel Courtenay's record of that battalion.
Captain Robertson of the Kimberley Light Horse was appointed Assistant Resident Magistrate at Koffyfontein, a small mining town in the south-west of the Orange River Colony. In the beginning of October 1900 there was a recrudescence of Boer activity in the district. Robertson found himself the only military man in the town, but he armed some fifty miners. On 12th October Commandant Viser demanded the surrender of the place, which was refused. On the 16th Robertson withdrew from the town and occupied a position at the mines which he entrenched. On the 21st the enemy attacked but did not press home. On the 23rd Robertson raided a farm-house occupied by the enemy, and a fierce hand-to-hand struggle took place. One man on each side was killed and two Boers were captured. On the 25th Hertzog demanded surrender and next day attacked fiercely, but the enemy was driven off. On 3rd November the gallant garrison was relieved by Sir C Parsons. Lord Roberts complimented Captain Robertson and his men.
Among the numerous columns at work during the second phase of the war was one known as the Kimberley Column, which for some months was composed as follows: 74th Squadron Imperial Yeomanry, 125; Kimberley Light Horse, 94; Dennison's Scouts, 81; Royal Welsh Fusiliers, 20; Volunteer Company of the Northumberland Fusiliers, 102; 3rd Leinsters, 100; 2nd Royal Scots Fusiliers, 38; 2 guns of the 38th Battery RFA; and 13 men of the Diamond Fields Artillery with a maxim. During 1901 this column under Major Paris long operated in the west of the Orange River Colony, and was also at work in the south-west of the Transvaal. On 2nd August 1901 Captain G C Gory Smith, of the KLH, was wounded at Zwartputs, and there were several other casualties on this occasion.