Complex sentence: When the calesa was introduced in the 18th century during the Spanish colonial period, it became one of the modes of transportation in the Philippines during the american period, Manila was teeming with kalesas, but after World War II they were not used in mass anymore.
Split into simpler sentences: When the calesa was introduced in the 18th century during the Spanish colonial period, it became one of the modes of transportation in the Philippines. During the american period, Manila was teeming with kalesas, but after World War II they were not used in mass anymore.