YOU ARE THERE: It is June 1918 and you are standing in an 8 foot deep trench on the Western Front in World War I. You are standing in about 6 inches of mud and cold rain water. You have mild trench foot and a nasty cold. You look down at your sleeve and you mildly regard your new chevrons for Sgt that where handed to you last week by your command officer, Lt G. S. Patton. He held a small staff meeting with you and the other Non-Commissioned Officers about an hour ago and told you that you will be leading the platoon "over the top" at precisely noon. You look at your watch and notice the time is exactly 11:58 a.m. Knowing that you will lose approximately 60 to 70% of your soldiers due to the enemy's machine guns in the first 5 minutes of combat, explain the leadership you will need to demonstrate to be successful in getting your troops out of the trench and on their way. Good luck!
First, it was highly unlikely that you would suffer 60-70% casualties within five minutes, which happens only in movies. It would more likely have taken 1-2 days to reach that kind of casualty level unless you were very unlucky. Second, if you were in Patton's unit you would not have been standing in a trench waiting to go over the top, you would have been standing next to a French-built Renault light tank waiting to follow up the poor, bloody Infantry because Patton was in one of the few tanks units of the AEF.
Formal answer below
The US Army defines leadership as influencing people by providing purpose, direction, and motivation, while operating to accomplish the mission and improve the organization. That definition has remained fairly constant with only minor changes for well over one hundred years. What that definition means in practice is slightly harder to describe and the definition does not say much about how to go about providing purpose, motivation, and direction.
In the context of World War I, leadership meant not just yelling "Follow me!", jumping out of a trench and charging across no-mans-land while trusting your subordinates to follow you. A whole host of actions and inactions by leaders went into building the trust of subordinates so that they would follow you. These actions included such things as training, ensuring the health and welfare of your soldiers by making sure they were fed, they got to the medics when ...
A description of the qualities of leadership required to motivate American soldiers to actively participate in battle