The primary reason Burgoyne’s forces became isolated was Poor planning.

The primary reason Burgoyne’s forces became isolated during the Saratoga campaign was poor planning. General John Burgoyne's strategy involved a complicated maneuver that relied on coordinating the movements of multiple troops along challenging terrain. However, his execution fell short, leading to a lack of timely reinforcements and supply lines. The British underestimated the resolve of American forces and overestimated their own capabilities, which left them vulnerable. This strategic miscalculation ultimately resulted in isolation, making it difficult for Burgoyne to maintain control and defend against the growing American resistance. The isolation of his forces contributed significantly to their eventual defeat at Saratoga.