Throughout EoC, the Cat army battles across various countries and cities to take over the world and recruits special units known as Legend units. Their inferred creator/leader is the fictional deity, The Cat God, who can be unlocked as a power-up early on in the story and as a unit upon further progression in the story. The story begins in the chapter Empire of Cats (commonly shortened to EoC), where an army of 'Battle Cats' travel the globe to conquer its nations. Additionally, the opening and ending dialogue to each saga is reused across all three chapters. They contain the same levels, theme, and treasures across all three chapters, with the only difference being the amount, difficulty, and selection of enemies that appear in individual levels.

There are ten chapters in all, but with the first three sagas, each chapter is essentially a reskin of the previous one. In total, there are 4 sagas in the main story, which each contain three chapters, except for 'The Aku Realms', which only has one chapter. Dialogue in the form of scrolling text before and after the completion of Chapters, unit and enemy descriptions, and battles during gameplay provide most of the game's lore and story. The plot of The Battle Cats takes place across four main story sagas, three subchapter sagas in the Legends Stages, and various miscellaneous stages. It was ported to the Nintendo 3DS in 2016 and Nintendo Switch in Japan in 2018 and Southeast Asia in 2021. A Microsoft Windows port was released in August 2017, and was available for download until late 2018, when PONOS Corporation ended support for it. It later was deleted from both the US Google Play stores and App Store, with an improved version released on September 17, 2014. The Battle Cats debuted on the Japanese iOS App Store in November 2012 under the name Battle Nyankos, with Android support following in December of that same year, and became popular in both Japan and Korea. The Battle Cats is a free-to-play tower defense video game developed and published by PONOS Corporation for iOS and Android, originally released in Japan under the name Nyanko Great War ( にゃんこ大戦争, Nyanko Dai Sensō).

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