The main reason for the decline of the Spanish Empire was a combination of military overreach, economic turmoil, and administrative challenges. The empire expanded heavily in the Americas, but maintaining control over vast territories proved difficult, leading to costly conflicts such as the Dutch Revolt and issues with indigenous populations. Economic difficulties, exacerbated by inflation from inflows of silver and costly wars, weakened Spain's finances. Additionally, ineffective leadership and corruption diminished the efficiency of governance, contributing to its gradual loss of power and territory by the late 17th century and into the 18th century.