Although the battle moved very rapidly over the terrain and involved large numbers of men and amounts of materiel, and although substantial casualties resulted, the officers of the AIF, any one of whom could have been killed at any second, amazingly found time to document the events in meticulous detail. Enormous quantities of the resulting documents have been put on line by the Australian War Memorial, even down to copies of the chits carried back and forth through the battle by messengers. I find it amazing that these bits of paper, some of which bore important tactical information ("Dense fog. Visibility 5 yards. We have lost sight of C Company. Are moving forward.....") and some of which were more in the housekeeping category ("Please send 10 rolls of white tape and pencils....") subsequently found their way into the archives rather than being simply scattered around the battlefield.

The Australian War Memorial archives include at two detailed summary documents, the First World War Diaries of the 16th Infantry Battalion, to which Thomas Casey and Ivan Guthrie belonged, and the First World War Official Histories. Excerpts from these documents are given below.

A good overall understanding of the battle is provided in the chapter Der schwarze Tag in the First World War Official Histories. The History of the AIF in France, referring to the battle on 8-Aug-1918 (see PDF pages 39 & 67 of “Der schwarze Tag” in http://www.awm.gov.au/histories/first_world_war/volume.asp?levelID=67892 ) states “By far the hardest task of the day on the Australian front fell to the 16th Battalion, which had to take the final objective in the northernmost sector beside the Somme".

Reference to the following map, taken from the Appendix to the 16th Infantry Battalion Diaries, is essential for a clear understanding of the advance from Morcourt to Mericourt in which Ivan Guthrie  and Thomas Casey fought and in which Thomas Casey was fatally wounded. The map shows three curved crayoned lines running roughly north-south: these are the objectives set for the Battalion on August 8, referred to in the narratives as the GREEN line, the RED line and the BLUE line, the latter being the ultimate objective for the day. These objectives were, in fact, accomplished. The blue crayon lines running roughly east-west show the movement of the 16th Battalion in a northeast direction towards Mericourt, i.e. parallel to the southern bank of the Somme river. 'D' Company, to which Thomas Casey belonged, is on the left flank of the advance. Note the town of Chipilly just opposite on the north bank of the Somme, i.e. northwest of Mericourt: German guns on the Chipilly spur, a steep wooded ridge, commanded a wide field of fire to the south of the Somme and were able to fire on the 16th Battalion's infantry and tanks at close range as they moved northeast towards Mericourt. It was probably a shell from one of those guns which hit Thomas Casey's tank, and the shell which subsequently fatally wounded him probably also came from there. The Germans' flanking fire held up the Australian Corps until late on the 9 August, when a small Australian party slipped across the river, and captured the village of Chipilly itself.

The accounts of the events of August 8th and of the preparations for the battle are highly evocative. Zero hour for the attack was fixed at 4.20am on the morning of the 8th. As the brigades and their vehicles and enormous amounts of materiel were moved up to the jumping-off points in the preceding days and nights meticulous precautions were taken to ensure that the Germans had little or no warning of the coming blow. Troops were told to move in small seemingly random groups by roundabout ways. Aeroplanes were flown over the area so that their noise would drown out the sounds of the tanks and lorries moving into position.  Diversionary attacks were carried out to confuse the enemy.

On the night of 4th/5th August 1918 the 16th battalion was moved into bivouacs on the banks of the river near Vaire-sur-Corbie (sic). Here it remained until the night of 7th/8th August when it was moved immediately after dark to the first forming-up place between Vaire-sur-Corbie and Hamel. (Taken from the Diary of the 16th Battalion).

During the night before zero hour orders were whispered rather than barked. Accoutrements and anything other items which clinked or rattled were muffled. Horses were calmed to prevent them from neighing. Talk was kept to a minimum to avoid information being picked up by German listening posts. The troops sat quietly smoking their Woodbines and preparing for the great event. According to the contemporary accounts morale was excellent.

At Zero Hour a thick fog lay over the area and as the battalions moved forward from their jumping off points, heralded by a massive bombardment of the German positions, they had the greatest of difficulty keeping in touch, maintaining the required positions relative to each other and making out the German positions ahead of them which they were to attack. As usual in an assault of this kind the Allied artillery, which was trying to "walk" its shells forward just ahead of the advancing troops to soften up the German positions (see the lines of trenches on the above map), was having difficulty ascertaining the positions of the Allied troops in the fog. Conversely, of course, the fog gave the infantry excellent cover as they advanced, in many cases surprising German units as the Australians overran (or stumbled into ?) their positions. One account in the Diaries mentions that a group of German officers was surprised at breakfast !

The fog cleared later in the morning but was to hamper the attack considerably in the first few hours. Nevertheless, the advances made by 10am that morning were prodigious. A contributory factor was surely the limited resistance of the German troops. The Diaries of August 8th and the succeeding days are full of accounts of German troops surrendering in large numbers to be marched back to the prisoner-of-war facilities in the rear with smiles and other expressions of relief on their faces. The Australian troops reported that the fire from German artillery, machine guns and other heavy weapons was intense but the resistance melted as soon as the fighting at close quarters began. One gets a feeling from these accounts that the majority of the German troops were quite simply exhausted by 4 years of war.

Infantry Company D, of which Thomas Casey and Ivan Gurthrie were members, was assigned to the third phase of the attack (between the RED and the BLUE objective lines on the above map). They attacked on foot and in infantry-carrying Mark V* tanks. These tanks were not battle tanks as we know them nowadays but rather armoured personnel carriers.

The abovementioned  http://www.awm.gov.au/histories/first_world_war/volume.asp?levelID=67892 when referring to the tanks says in a footnote on p.68 “Like those allotted to other brigades eight of these tanks carried as passengers 8 officers and 112 other ranks of the AIF with 10 Vickers and 16 Lewis guns, an average of 15 passengers each beside the normal crew of eight". There was a ninth tank in reserve. They were by all accounts underpowered, unreliable, cramped, hot, noisy and fume-filled even before they were shot at. The Diaries describe how Company D moved forward to their assigned part of the assault in the fog and under artillery fire, with the officers in the tanks peering out of little slits and trying to find the way and "steering" the drivers  by tapping on their shoulders. Time and again they would find themselves moving up a hill or over terrain which the tank, with its underpowered and overheating engine, could not manage and they would have to turn back and try another way. For much of the advance the infantry preferred to walk beside their tanks and risk the enemy fire rather than endure the discomfort inside. If I have read/interpreted the Diaries correctly, many of Company D's tanks had quit by the time the unit reached the third phase of the attack to which they had been assigned.

For the assault phase between the RED and the BLUE lines the Battalion had only 4 tanks left and another tank, a Mark V, was picked up to accompany them. Up to the RED line the casualties had been few but between the RED and BLUE lines, the segment to which Thomas Casey's and Ivan Guthrie's 'D' Company had been assigned, they mounted under the withering fire from the German positions on the hill on the opposite banks of the Somme.  Four tanks were put out of action by the German guns before reaching the BLUE line, one when crossing the RED line, two in Q.18.c, and  the fourth in Q.17.b (these map coordinates can be found on this map).  The fifth got as far as the BLUE line near Mericourt but was there put out of action and most of the crew were killed. This latter tank was probably the one which carried Thomas Casey and which he abandoned to advance with his Lewis gun.

The casualties between the RED and BLUE lines amounted to 40% of the Battalion strength and included Thomas Casey.

Captain W.J.Lynas, D.S.O., M.C., O/C of 'D' Company, wrote the following account of the advance of his tanks which contained Thomas Casey and Ivan Guthrie (they may have been in the same tank but we cannot be certain of this):