Final answer:
Forts built by the federal government did not always protect settlers due to familiarity of the land by Native Americans, violation of treaties by settlers, government corruption, and mismanaged policies causing conflicts. The settlers' encroachment on Native lands made the forts targets and prompted Native American resistance, contributing to the ineffectiveness of these forts.
Step-by-step explanation:
The forts built by the federal government were not always effective in protecting settlers from Native Americans for several reasons. Firstly, Native Americans were familiar with the land and could escape easily if attempts were made to enslave them for labor purposes. Secondly, the White settlers often violated treaties that had been established with the Native Americans, which were poorly enforced by the federal government. Additionally, government corruption and mismanagement led to many Native Americans not receiving promised payments, causing destitution and leaving them with little reason to respect the boundaries set by treaties.
As settlers expanded west, they increasingly moved onto lands designated for Native Americans, causing conflicts and confrontations. Many forts became targets due to this encroachment. Settlers often attacked Native American tribes out of fear or to force them from the land, and in turn, Native American resistance to such aggression often made the forts less effective as protective structures. The overall strategy of the U.S. government shifted towards moving Native Americans onto reservations, which in itself was a source of conflict. In summary, the complexities of westward expansion, violation of treaties, settler aggression, and ineffective governmental policy resulted in the fort system's inability to fully protect settlers from Native American resistance.