Alderamin on the Sky Nejimaki Seirei Senki: Tenkyou no Alderamin

The Katvarna Empire is at war with the neighboring Republic of Kioka. In the Katvarna Empire, the lazy, woman-admiring Ikuta hates war, but due to certain circumstances, he grudgingly takes the High Grade Military Officer Exam. No one would have expected that this 17-year-old young man would eventually become a soldier called a great commander by others. Ikuta survives this world engulfed in war with his superior intellect.

(Source: Anime News Network)