How did gliders take off in World War 2?

During World War Two gliders were used for training and military operations. For training purposes the glider would be pulled into the air by a Jeep with a winch on it, or a motorized crank in more simple terms. For combat deployment gliders would be attached to tow wire behind large bombers and when they reached the correct altitude the bomber would disconnect the gliderb. However gliders used for this purpose were about 25 feet long and could carry around 30 or more soldiers. Gliders were used to drop troops behind enemy lines usually when enemy defenses were very high, ex. D-Day.