The battalion was in position for the attack by 3:30am, a hot meal and rum was then issued before watches were synchronised, briefings carried out and final preparations made. The men now lay in total silence, waiting to launch themselves forward into the enemy trenches opposite. Five minutes before zero hour (5:30am), word was passed along the battalion line to fix bayonets and get ready. British artillery opened fire on the enemy line at exactly zero hour, the first wave of Seaforths moved off immediately the barrage began, moving forward in double waves as practised. The men moved through the British barbed wire cut earlier, forming up in attacking waves under cover of the bombardment that was taking place. The artillery was extremely accurate over on the right, in the centre the first wave got within 10 yards of the enemy positions, on the left to within 20 yards. No shells fell short as the Seaforths waited for the artillery fire to lift so the advance could continue; the barrage then moved on to the second line at zero hour plus 4 minutes.

As the shellfire moved on, the Highlanders rushed forward and stood on the enemy parapet shooting the German soldiers as they came out of their dugouts. The Battalion War Diary says that this was a very effective way to deal with defending troops, most of the enemy dead were found to have been shot in the head. The First Line of enemy trenches was soon taken with few battalion casualties; on the left flank however a number of enemy soldiers managed to reach shell holes and begin sniping at the advancing Highlanders.

The snipers caused several casualties before they were dealt with, a good many enemy soldiers were also killed on the right flank as the battalion continued its advance. A German officer on the right who killed two Seaforths after raising his hands to surrender was shot; the men then cleared a well-constructed tunnel untouched by the shelling.

The second double wave now moved forward through the first wave, some time was lost as they crossed the heavily damaged enemy First Line trench, the men having to lower themselves into the trench then climb out the other side. The barrage on the enemy second line had only lasted three minutes and proved to be too short, as the Seaforths climbed from the enemy First Line they came under heavy rifle and machine-gun fire. Some casualties now occurred before the Highlanders gained the enemy Second line trench on the left flank, making contact with the 9 Royal Scots. The attacking waves now began to work their way up the communication trench dealing with any defenders quickly, little resistance was met in the centre but on the right flank heavy losses occurred.

Fire on the right came from an enemy machine-gun post in a communication trench and snipers lying out in the open; parties of Seaforths who captured the machine-gun post and killed the crew quickly dealt with this opposition. The snipers in the open ground were also attacked with great skill and killed, very few prisoners had been taken so far.

The attack had now been taking place for twenty minutes and had been a success, touch had been made with the British units on both flanks and the attack was going well. Enemy wire cut by the barrage formed no obstacle to the attacking Seaforths, defending enemy troops had been taken by surprise and battalion casualties were relatively light.

As the battalion moved on to assault the Third line a shell burst in the assembly trench causing 15 casualties, again good progress was made on the left. As the attacking waves moved off from the Second line they were halted by machine-gun fire from their right which appeared to come from the Black Line. The advance was now stopped, it was impossible to move due to the volume of fire falling on the attacking wave.

In the centre Second Lieutenant Spence and forty men had kept close to the barrage and had managed to get into a Switch trench to bomb some dugouts, two prisoners were also taken. This party got into the Black Line at zero hour plus 34 minutes and with N.C.O.s joining from the right flank began to deal with snipers until 7am. A firm hold was now established in the third line trench, however as the party of N.C.O.s consolidated themselves the enemy blew a booby trap mine, which only caused enemy casualties no Seaforths were hurt.

Heavy fighting now took place in the Black Line until touch was made with units on the flanks at 7:30am, it was not until 9am that all enemy soldiers in the centre had been dealt with, either killed or were prisoners. On the left flank two enemy machine-guns caused heavy casualties, Second Lieutenant Read collected some stragglers he found from the 7 Argyll & Sutherland Highlanders then outflanked the Germans guns, killing all the crews.

Only one officer from the wave to assault the Black Line reached the objective, all other officers were killed or wounded. The Battalion War Diary says “great credit goes to Second Lieutenant C.L. Read and the N.C.O.s from ‘B’ and ‘D’ Company who fought so gallantly, finally taking the objective.”

At 7am a British contact aeroplane flew overhead to see if the objective was secure and sounded its contact horn, no one from the Seaforths heard the horn due to artillery fire in the confusion and noise of battle. The Seaforth Highlanders lit flares on the left to say the objective was secure and by 11am the troops in the Black Line were in telephone communication with Battalion Headquarters. The objective was now secure and the men from the 6 Seaforths began to establish their new positions, digging in to prepare for an enemy counter-attack. The Highlanders found the enemy trenches to be well built with plenty of bread lying about but no meat and very little butter. Enemy dead littered the ground at the junction of the Communication Trench and Second Line trench, where they had been killed by battalion Lewis gunners as they fled.

Battalion booty, consisting of two machine-guns; five trench mortars and many letters, maps and documents were sent back along with the one hundred and fifteen prisoners captured. The 6 Battalion Seaforth Highlanders took casualties of four officers killed, five were wounded, one hundred and forty-one other ranks were also killed, with one hundred and seventy-six men wounded most only slightly; two men were reported as missing.

The Battle of Arras continued until June for no real gain and with no breakthrough, the final cost was 150,000 British dead, wounded and missing. The year of 1917 took on a sombre look, the French Army in the south was close to mutiny and Russia collapsed in revolution, only Britain was strong enough to carry on the fight. Private Angus Gunn Mackay was on of those killed in action on the 9 of April 1917, as the 6 Seaforth attacked the German lines in the Roclincourt Valley, he was twenty-four years of age. (See also Donald John Mackay, Modsary and John George Mackay, Clashnastruag.)

Angus had a brother William who served with the Royal Naval Reserve on H.M.S. Albion he survived the war to return home to Skerray.