Solution:
The most powerful weapon of the Spanish conquerors was not a conventional military. It was a disease called smallpox which proved to be a deadly killer. These were assumed to be brought by the Spanish to the place needed to conquer. Natives of America and other countries were not liable for this disease. This deadly disease wiped out the entire city population. During that period, the immune system was not strong. Conquerors achieved their main target of colonising the country without using conventional weapons. This way of colonisation had the worst effect on the mental health of the population.