Twelve attacking battalions, including the East Kent, West Kent, Queen's West and East Surrey Regiments, lost 8,000 out of 10,000 men in just four hours of fighting on Sept 26, 1915. The 8th Bn The Buffs (East Kent Regiment) was virtually wiped out.
The Battle of Loos was the largest British battle on the Western Front during WWI and the casualty figures rivalled the horrors of the first day of the Somme.
Kent's small rural farming communities were hit hard with many villages and hamlets left grieving the loss of their young men.
One of them was Sgt Arthur Harrison, of Newington, near Sittingbourne, who will be commemorated by Newington History Group and the village primary school on Monday (Sept 28) - the centenary of his death.
Sgt Harrison enlisted in Chatham in 1910 and fell in the Loos battle aged 23. The pupils have been learning about his family life and years in the 2nd Bn The Buffs (East Kent Regiment). They will present the History Group with a small cross with Sgt Harrison's name on it to be placed at the village's war memorial.
British casualties in the main attack at Loos were 48,367 and 10,880 more died in the subsidiary attack - about twice as high as the German casualties. It represented 59,247 of the 285,107 British deaths on the Western Front that year.
It was the first time the British used poison gas - a move that backfired when wind blew much of it back over our own trenches - and was the first mass engagement of Kitchener's Army units. The battle was part of the attempt by the Allies to break through the German defences in Artois and Champagne.
The initial advance over open fields on Sept 25 was within range of German machine guns and artillery. In many places British artillery had failed to cut the German wire in advance of the attack, leading to the devastating losses.
Though the British were able to break through the weaker German defences and capture the town of Loos-en-Gohelle, supply and communications problems, combined with the late arrival of reserves, meant that the breakthrough could not be exploited.
The Germans had recovered and improved their defensive positions by the time the reservists arrived and the battle resumed the following day.
However, as WWI researcher Kyle Tallett, from Ashford, says: "The reservists (the 8th Bn) arrived in France - untrained and unacclimatised - and were marched straight into battle. They hadn't even had dinner!"
The 8th Bn arrived in France on Sept 1 and were sent to the concentration area for the Battle of Loos on Sept 21 before being marched to Bethune on Sept 25. They were told to move to Vermelles for an attack that night which was postponed until the following morning.
Detailing the battle, Mr Tallett says: "The unit had only been in France for three weeks, hadn’t done it’s apprenticeship in the trenches as was customary plus it had marched hard to get to the start point without rations.
"The Germans started shelling. The Buffs withstood this for four hours before withdrawing taking casualties as they withdrew. They were relieved that night, but the casualties were staggering. Only one officer was left alive to bring them out. The casualty figures were 24 officers and 610 other ranks.
"It was a similar story with the West Kents, Queens, and East Surreys. The battalion was virtually non-existent within three weeks of landing in France. The Division, the 24th never recovered, and had to have a regular brigade attached to it to stiffen it up. The truth is they were not taught to fight and never saw a trench until the attack."
By Sept 28 the British had retreated to their starting positions. Further fighting during October was hampered by fog, a lack of hand grenades, heavy rain and accurate German shelling as the losses mounted up.
The 6th Buffs, with three month's experience to draw on, were committed on Oct 13, also at Hulluch. By a cruel coincidence they clambered over the killing fields of their sister battalion.
The Kent men crossed no man's land to find the wire uncut and were machine gunned before they could retreat. Ten of the 13 officers were killed along with 450 other ranks.
Mr Tallett says Loos was Kent's equivalent of the first day of the Somme but is not as well known. "Our divisions were wiped out at Loos - a good seven months before the Somme - with casualty figures that rivalled the first day of the Somme on July 1, 1916.
"If the casualties of the 8th Buffs had occurred on that day they would have been second in the table for most casualties sustained. The 6th Buffs would have been in the top half.
"In terms of proportion to Kent's rural communities it was every bit a disaster."
The Loos Memorial commemorates over 20,000 soldiers who fell in the battle and have no known grave - including Sgt Harrison.