Trenches were used in some of the earliest battles on the Eastern Front. Here is the account from Grenadier Regiment Nr 4, taken from 'Geschichte des Grenadierregiments König Friedrich der Große (3. Ostpreußisches ) Nr. 4'. The regiment was part of Falk's 2nd Infantry Division on the German left wing during the Battle of Gumbinnen. The translation is mine, as are any mistakes therein:
"Stirnlaugken was reached early in the morning of August 20. As a result of this advance, a Russian NCO post was taken by surprise and captured. The high ground around Ederkehmen [near Mingstimmen] was occupied by the Russians.
Our regiment was positioned on the extreme left flank of the 2nd Infantry Division to attack Werdehlischken. Storming forward, Fusilier- and II. Battalions captured Ederkehmen and Henskehmen. I. Battalion cleared [the village of] Abschruten of weak enemy forces and then extended the line of the regiment to the northeast.
Some sections were diverted to search farmsteads, under Unteroffizier Braun from 8th Company. As he was pushing forward, he spotted an enemy battery moving up. He ranged in a beaten zone at 1200 to 1300 metres, which brought down some of the horses. Two guns had been set up in position, firing off a couple of rounds. After a short burst of fire from Braun's detachment, the gun crew was rendered hor de combat, silencing the guns. Brauns called in artillery fire on some farms from which Russian infantry were firing, next to the Russian battery, setting them on fire. He then pushed forward with his riflemen towards the battery. He found the gun crew, about 50 men including three officers, sheltering under the guns. They surrendered. The guns were rendered useless by destroying the breechblocks.
After repulsing a fierce Russian counterattack near Mingstimmen, the regiment was holding firm in front of the line Wannagupchen – Mingstimmen by the afternoon. The right flank of the Russians was retreating hastily to the east. A large number of prisoners were taken.
Already during this fighting the Russians had shown themselves to be masters of the art of field fortifications. Their defensive locations were so well distributed and so skilfully blended in that you had to standing literally right next to the front of them in order to see them. The Russian [soldier] proved tougher in battle; his field craft and ability to shoot was up to the standard of a well-trained enemy. As soon as the German [soldier] came into close quarters contact, however, many Russians suddenly lost their resolve. Some fled from the trenches, others raised their arms and rifles high and begged for their lives saying "they were also Christians". Only a few would stand against an attack going in with the bayonet. The Russian field artillery fire was superb, albeit wasting great amounts of ammunition. This arm was, and still is, the elite troops of the enemy.
Late in the evening, the victorious troops received a completely surprising order to retreat immediately, which the front-line soldiers could not understand at first."
Robert