The answer is Precipitation
The victory at Cowpens gave the Americans more confidence.
The battle win completely turned around the American morale and gave them a renewed sense of confidence that they could actually go on to win the American Revolutionary War.
My dearest wife,
I've been through hell and lived to tell the tale. I cannot wait to crawl back into your arms, having witnessed this... massacre...friends dying left and right, brothers screaming for help...but only the roar of the guns was heard.
It's been the largest number of casualties I've even seen in my life...and oh God... I hope no one ever sees hell like this again.
We, the Union, have somehow defeated general Lee, and stopped the invasion.
I hope to see you soon,
Yours forever, Erik
This is called trench warfare!
The name comes from the trenches, that is the ditches that the soldiers built.
This warfare was typical in the First World War and it led to frequent stalemates: the trenches are easy to defend but hard to attack so for long periods of times the front remained stable.