Complex sentence: By World War II, a number of specialized aircraft were developed to fulfilll the role, but often strike fighters and fighter-bombers were used e.g. in the Korean War, tactical missions were carried out by WWII-era fighters such as the F4U Corsair.
Split into simpler sentences: By World War II, a number of specialized aircraft were developed to fulfilll the role, but often strike fighters and fighter-bombers were used. For instance, in the Korean War, tactical missions were carried out by WWII-era fighters such as the F4U Corsair.