Title: Understanding the Success of Knowledge Distillation -- A Data Augmentation Perspective. Abstract: Knowledge distillation (KD) is a general neural network training approach that uses a teacher model to guide a student model. Many works have explored the rationale for its success. However, its interplay with data augmentation (DA) has not been well understood so far. In this paper, we are motivated by an interesting observation in classification: KD loss can take more advantage of a DA method than cross-entropy loss \emph{simply by training for more iterations}. We present a generic framework to explain this interplay between KD and DA. Inspired by it, we enhance KD via stronger data augmentation schemes named TLmixup and TLCutMix. Furthermore, an even stronger and efficient DA approach is developed specifically for KD based on the idea of active learning. The findings and merits of our method are validated with extensive experiments on CIFAR-100, Tiny ImageNet, and ImageNet datasets. We achieve new state-of-the-art accuracy by using the original KD loss armed with stronger augmentation schemes, compared to existing state-of-the-art methods that employ more advanced distillation losses. We also show that, by combining our approaches with the advanced distillation losses, we can advance the state-of-the-art even further. In addition to very promising performance, this paper importantly sheds light on explaining the success of knowledge distillation. The interaction of KD and DA methods we have discovered can inspire more powerful KD algorithms. 