Which is an example of a union strategy that took advantage of a confederate weakness

Brute force - The North had strength in numbers, this was Grant's favorite strategy, overwhelm the enemy with overwhelming numbers to match the South's lack of men in most cases. Another was the Anaconda plan, where they planned to take advantage of the South's weak navy, and use their superior naval forces to choke off the South's ports, therefore, cutting off their supply lines and trade ports, thereby cutting off the South's income as well as supply from trade.

South carolina was so angry about the election of lincoln that they seceded from the union on december 20, 1860. they attacked fort sumter later, on april 12, 1861.