Recoil leaders develop in lightning flash decayed channels. The propagation of a recoil leader depends on its intensity and on the conductivity of the decayed channel. When the recoil leader is strong enough to propagate over the entire channel, a subsequent return stroke happens. When the recoil leader is not intense enough, only a partial reconstruction of the channel occurs, that is, only part of the decayed channel is reionized. The present work aims to analyze the herein named secondary recoil leader that originates near a previously formed recoil leader. When these secondary recoil leaders develop and connect to previous recoil leaders, they provide enough energy for the recoil leader to reionize the whole decayed channel of the lightning flash. High-speed videos analysis of upward lightning flashes shows that secondary recoil leaders play an important role on the formation and progression of dart leaders/subsequent return strokes.