The latest attack at Ypres takes place today, an attempt to further extend the Allied position with Poelcapelle at the centre of their crosshairs. The last few attacks have been relatively successful, with ground gained and significant casualties inflicted on the Germans (albeit also at considerable cost to the Allies).
Good weather played a significant role in previous successes. Now however the weather has broken. British airmen find it harder to observe and guide down artillery on German positions. The infantry find if extremely difficult to move forward across an increasingly muddy battlefield. Mud also makes it difficult to keep the guns firing. And the tanks find themselves unable to manoeuvre in the morass into which they are to advance.
The result is that the British and their Commonwealth allies suffer terrible casualties and make almost no gains. The only real success today happens on the British flank, where French troops trudge through the mud behind a slowly creeping barrage, achieving their limited objectives with relatively few casualties. Overall this is a day of failure, though British commanders may at least take some satisfaction from the knowledge that the Germans too have suffered great losses in containing the attack.
Mud (Copwick: images of Poelcapelle and the Passchendaele battle site)