I read it in one of my books about the battles as a quote. This was a reference to combat methods used by the Latvians. Many people do not know about the bloody Eastern front or WWI except what TV or movies show and Hollywood never gets it right.
Normal trench combat methods in this era was for one side bombing the hell out of the enemy trenches and then charge out and hope to disperse the enemy. This would inform the enemy that an attack is coming and to be prepared. At Gallipoli, the Turks would leave the trenches when the bombardment started and immediately return after it stopped, return to stop the attackers. A quote from a Turk General at the battle site states, "If they had shot behind our trenches we wouldn't be alive today"
If you read the Daybook, you would notice training in silent crawling, getting out of the trenches quietly. Unless ordered by the Russian Command, the Latvians would leave their trenches silently with no bombardment, at night and crawl up to the enemy trenches and when the line was close enough they would all arise shouting "URRA" and jump into the enemy trenches with bayonets. The surprised Germans trying to flee would be blow up by Latvian artillery that opened up and raked the area behind the German trenches. The front lines barely moved in Latvia from 1915 until the Christmas battles in 1917 when the Russians replaced the Latvian Line and the start of the Russian Revolution.
This started a dark side of the Latvian Riflemen for Lenin and the communists hired a group, which I will not mention, as their bodyguards for they did not trust their own soldiers. At one time, they had complete control of Moscow and when the Whites attacked them, they retreated into Lubyanka Prison with Lenin and held them off for over 30 days until help arrived. They eventually got disillusioned with the Communists, returned to Latvia, and fought the Communists trying to regain Latvia. Latvia has a military history that goes back many centuries that is not known in the western word but is slowly being presented by scholars and books. Latvian history books still tell of the first defeat of Germans invading the Latvian territory in 1231 by the Letts.
History is what we repeat if we don't study it.