"Unlawful War; Letters of a Spaniard" is a collection of letters by the famous Spanish author Armando Palacio Valdes, which was written during the socio-political upheavals in Spain. In his letters, the author expresses his vision of the injustice of war, moral doubts about the conflict and seeks to condemn violence as a way to resolve conflicts. Readers are encouraged to think seriously about the ideas of war and peace, justice and injustice, and active citizenship in the modern world. The book "Unlawful War; Letters of a Spaniard" is not only a literary masterpiece, but also a call for wise reflection and peaceful resolution of conflicts in the modern world.