What failure of Union General William Butler had an ill effect on Union war efforts in June of 1861?

In June 1861, Union General William Butler failed to capitalize on the opportunity to seize control of the Confederate stronghold at Fort Monroe and advance into Virginia. His decision to remain largely inactive allowed Confederate forces to regroup and strengthen their positions. This inaction contributed to missed opportunities for the Union, ultimately delaying their advance and prolonging the conflict in the early stages of the Civil War. Butler's failure highlighted the challenges of leadership and strategic decision-making that would plague the Union Army in its early campaigns.