What was two unexpected events brought Grant's campaign against Vicksburg to a halt?

Two unexpected events that halted Grant's campaign against Vicksburg were the severe flooding of the Mississippi River and the unexpected strong resistance from Confederate forces. The flooding disrupted supply lines and troop movements, while the Confederates, under General Pemberton, fortified their positions, making it challenging for Grant's army to advance. These setbacks forced Grant to rethink his strategy and delayed the campaign's progress.