Twenty-one thousand men were deployed to push through to Ladysmith via Colenso, the largest force utilised by any British general since the Crimean, taking in artillery, mounted infantry and regular footsoldiers. The four and a half thousand Boer commandos held the ground to the north of the town and the railway station, and had dug trenches on flat ground by the raging, unpredictable Tugela River. The trenches had been successful at Magersfontein, keeping the occupants safe from artillery fire. British success depended on enough of Buller’s men managing to get across the river and establishing a bridgehead to allow others to cross safely. There were few places to cross the violent Tugela, and Buller was pessimistic about his chances of victory. Everything would depend on selecting the proper tactics and his generals following them to the letter. The plan would involve three attacks: Colonel Dundonald and the mounted infantry would attempt to take control of Hlangwane Hill on the right flank; Major-Gen. Hart and his Irish Brigade would storm the small Bridle Drift on the left; Colonel Hildyard’s 2nd Brigade would launch the main attack at Old Wagon Drift near the rail bridge.

The morning of the 15th gave Buller a nasty surprise. Hildyard’s force was to be supported by Colonel Long’s artillery from a distance outside the range of the Boers. The infantry major designated to protect Long was surprised on the march to the Tugela to see Long’s gun teams rattling past them to the frontline. He sent several messages demanding to know what was going on, but received no reply. Long passionately believed that, “The only way to smash those beggars is to rush in at ’em,” and deliberately ignored Buller’s cautious strategy, setting up less than 700 yards from the Boers in open territory. As soon as the Boers noticed Long’s mistake, a thousand Mauser rifles concentrated fire on the twelve field guns. With no infantry to protect them, the gunners suffered a heavy toll. When a third of the them had been killed or wounded, the decision was made to move the survivors into a nearby hollow for shelter, abandoning their guns. Without the covering fire to protect them, Hildyard’s force held back.

Meanwhile on the left flank the Irish Brigade had gone the wrong way. Hart’s map depicted Bridle Drift a mile to the west of a great loop in the river, but his African guide insisted the only crossing was actually at the loop. Sending men into the open end of a loop was asking for trouble, as Boers heavily guarded the three sides surrounding the loop. Ignoring the map, he took the guide’s advice and led his forces into a death-trap. The loop was only a thousand yards wide, and the four thousand men marching into it were unable to spread out to protect themselves from the accurate enemy fire.

By chance the 1st Inniskillings had made their way along the river to the real crossing point, but a furious Hart ordered them back to join him. Artillery set up to provide covering fire for Bridle Point had to quickly reposition to help Hart’s men, but with no time to calculate the new targets properly, a lot of their shells fell short into the men they were trying to protect. Some of the soldiers were faced with no other choice but to throw themselves on the ground and wait until the order to retreat was given. Bugler Dunne, a fourteen-year-old with the Dublin Fusiliers took it upon himself to sound the advance, whereupon a number of his comrades fixed bayonets and tried to cross the ten feet deep river, and were shot down. Dunne was wounded himself, and on his return home he became a great hero for his reckless acts.

Buller watched the mayhem in disbelief, his carefully formulated plans falling apart through his officers’ carelessness. He told Maj. Gen. Lyttleton: “Hart has got himself into the devil of a mess down there: get him out of it best as you can.” Buller reluctantly ordered his men to withdraw, cursing the fact that the battle had been lost before the majority of his troops had even been brought into the fray. Furthermore, the abandonment of Long’s guns was a cardinal military sin, and he needed to bring them back. Riding over to the remnants of Long’s men, he asked, “Now, my lads, this is your last chance to save the guns; will any of you volunteer to save them?” So revered was Buller among his men, two groups were formed from the gunners and Buller’s own staff. As the volunteers rode toward the guns they came under heavy Mauser fire from the Boer side. Some, including the only son of Lord Roberts, were killed immediately, but two of the twelve guns were brought back. That was as good as it got for Buller that day, and further rescue attempts failed to retrieve anything else.

In his initial report for the benefit of the press, he refused to blame any individuals, but privately Buller was furious with Long. Buller was heavily criticised for his tactics. He failed to notice the overwhelming importance of capturing the 3614 feet high Hlangwane Hill, which would have given him a huge advantage. Dundonald’s forces were designed as a diversion to occupy the attention of the enemy while Hart and Hildyard pushed through. Eyebrows were raised again at the War Office when a private communication from Buller came through: “I do not think I am now strong enough to relieve White. Colenso is a fortress which I think if not taken in a rush could only be taken by a siege… My view is that I ought to let Ladysmith go, and occupy good positions for the defence of Natal.” Despite outnumbering the Boers by five to one, Buller was complaining it was not enough. Even worse, he seemed to advocate leaving the people of Ladysmith to defend themselves. Buller then sent a heliograph message to Lt-Gen. White at Ladysmith: “Can you last long? Stop. If not, how many days can you give me to take up a defensive position, after which I suggest your firing away as much ammunition as you can, before making the best terms [of surrender] you can. Stop.” On receiving the message, White was convinced it was a trick message from the Boers.

The casualty toll and the ten guns abandoned were a small percentage of his total force, but the War Office could not ignore the effect that Black Week had on the nation’s morale. The events at Colenso wrecked any lingering hopes that the campaign in South Africa would last a few months, and preparations were made to set out strategies for a drawn-out war. The first necessity was to find a replacement for the increasingly erratic Buller as Commander-in-Chief.