^ these answers I've given should be pertinent
Controversies surrounding strategy, manpower and morale affected the decision making of the major continental powers in WWI. In the case of the Western Front, soldiers, commanders and politicians responded in different ways. For the soldiers on the ground, morale and cohesion were vital to unit performance, and various ingenious ways were developed by soldiers to cope mentally with the pressures of battle and the monotony that characterized most time in the firing line. Alexander Watson describes some of these mental coping strategies [here] (https://web.viu.ca/davies/H482.WWI/SelfDeceptionSurvivalSoldiers.WWl.pdf), and his book Enduring the Great War is an excellent examination of how British and German soldiers survived in the trenches. Although the understanding of losses in other units may have been limited for soldiers, the influx of replacements (or lack thereof) after heavy periods of fighting would have been a rather explicit gauge of the intensity of the fighting.
Wider manpower and morale issues would have been better understood by Politicians and Commanders, who had (in theory at least) a grasp of the 'big picture', and access to information from recruitment reports, morale evaluations based on unit inspections and mail censor reports, etc. Leonard V. Smith's book on the French Army Mutinies, Between Mutiny and Obedience, is an excellent source for examining a French unit, the 5th Infantry Division, and it's reactions to the losses of 1914-16, culminating in Mutiny in 1917 following the failed Nivelle Offensive. In the case of the Mutinies, responses from the top and the bottom can be discerned. At the top, the grandiose scheme of the Nivelle Offensive was a reflection of the French High Command and Governments awareness of the affect that losses were having on army reserves and morale. In response to this, Nivelle was allowed to plan a breakthrough, promising one in 48 hours that would collapse the Western Front. This failure lead to the Mutinies and to Petain's promotion to command the Army. Afterwards, French offensive actions comprised of limited depth, set-piece attacks, something which was already being done before, but which was now made the standard tactical/operational method of the French Army. French units in the Mutiny also affected change, with officer-man relations often reflecting the Republican institutions of France itself. Attacks were limited to only what unit commanders and their men thought was feasible, and attaining consensus was an important job for French officers with their men.
British responses were somewhat similar. The British began utilizing set-piece attacks during the Somme offensive, when it became clear that a through-and-through rupture as had been hoped for in 1915 by the allies was going to be elusive. With the launching of the Flanders Offensive in 1917, Field Marshal Haig advised that General Gough's 5th Army should adopt a step-by-step approach, with a breakout from the Salient towards the rail lines at Thorout-Roulers being attempted only after the Germans had been cleared from the ridge lines of Passchendaele-Staden Ridge, the Gheluvelt Plateau and the Messines-Wytschaete Ridge. Gough's attacks at Pilckem Ridge and Langemarck, however, were probably deeper than they should have been, and combined with poor weather this made for difficult going and with heavy losses. When the year ended, there was a shakedown in the British War Cabinet and at BEF HQ, and all the Allied Armies were subordinated to a Supreme War Council, allowing the civilian governments more control.