War and diplomacy can be seen as two opposite ways of doing politics. War involves the use of violence to impose one?s position, while diplomacy is the negotiated way to reach a consensual solution, using the motive to reach an agreement valid for all parties. On many occasions, it has even been seen how the recourse to war implied the failure of diplomacy and negotiation. However, throughout history, some intellectuals, whether political or military, have proposed different points of view of that relationship, arguing that war and diplomacy are, in the end, different weapons that follow the same objective. In the present work several historical analyzes are collected, which focus on the scope of the Iberian Peninsula and the late medieval period, and show how diplomacy and war often involved different, and sometimes parallel, ways of achieving political objectives. Presenting Portuguese, Castilian and Aragonese visions, a series of diverse cases is shown that, in effect, the utility of both forms of policy exercise was parallel, and as such was used by the various political powers.