This article explains well why we need attention: https://jalammar.github.io/visualizing-neural-machine-translation-mechanics-of-seq2seq-models-with-attention/

This article explains well why we need attention: https://jalammar.github.io/visualizing-neural-machine-translation-mechanics-of-seq2seq-models-with-attention/ https://jalammar.github.io/visualizing-neural-machine-transl..., and also how it was developed.