Question

An attack where a military force surround a city or fort in order to make them surrender

Answer 1

The answer is siege.
Siege, also known as blockade or encirclement, is an attack where a military force surround a city or fort in order to make them surrender. This would trap the enemies with the force encircling them. The force basically encircles them then cuts off their resources and supplies and compels or persuade them to surrender.