Koei Tecmo Games started the official OPEN Beta test of the Nobunaga’s Ambition -Oretachi Sengoku- smartphone game in Japan. The OBT runs until October 14, 2016 (14:59 local Japan time) and you can try it with iOS and Android devices.
The recommended devices is minimum an iPhone 5s with iOS 8.0 or an mid/high-end Android device with Android 5.0 or higher (except some local Japan models) BUT it runs on iOS 7.0 and Android 4.2 too but you maybe have to face with some problems.
It should be noted that if you clear and send the opinion box after the test you will get extra gifts when the official service starts.
After the first pre-registration event, Koei starts a new one (if you registered in the first campaign you will get your gifts) where depends on the registered users number you can get more, new warlords! The details of the new pre-registration campaign can be found on the official website.