The corporal does not inspire much confidence because he does not seem to know or care what he is doing.
Jonathan wants to join the militia so he can fight the British. He does not wait for his father to give him permission. He just goes. Unfortunately, the corporal he ends up under does not really inspire confidence.
The men seem concerned about the corporal because he does not know what they will be facing. He seems overconfident without bothering to get any actual information.
“How many do you think they’ll be?” called a man.
…Twenty, twenty-five” came the Corporal’s offhand reply.
His words were met with uneasy silence….
“Before, you said there weren’t more than fifteen” came an angry voice. (12:05, p. 20)
The men are already beginning to doubt the Corporal when they have only just begun. Even young Jonathan is aware that the glances the men exchange mean they don’t have confidence in their leader. Who can blame them? The Corporal's combination of arrogance and laziness does not inspire much hope that he is going to be able to lead them or even keep them alive.
Jonathan is beginning to see that figthing is not as romantic as he thought it was going to be.