Ileso translates to "unscathed" or "unharmed". It's a powerful word that implies surviving a dangerous situation, like a battle, without any injury.
In "Besos en Guerra" (Kisses in War), the singer uses this war metaphor for love. He sings, "Y tú nunca juraste que saldría ileso" (And you never swore that I would come out unscathed), poetically admitting he knew from the start that this risky love affair would likely leave him with a broken heart.
Morat and Juanes give us a song that treats love like an all-out war. The singer is a soldier who knows from the very beginning that he's probably not going to make it out alive. He tells his lover he always knew that "tus besos matan" (your kisses kill) and that she's an expert at stealing his heartbeats. There are no illusions here; he went into this relationship with his eyes wide open, fully aware of the danger.
Despite the pain, he has zero regrets. He says, "Yo te confieso que no me arrepiento / Y aunque estoy sufriendo podría estar peor" (I confess that I don't regret it / And even though I'm suffering, it could be worse). He refuses to give up, declaring that he will "Ganaré la guerra para conquistarte" (I will win the war to conquer you). It's a dramatic and passionate song about choosing to fight for a dangerous love, even if it means you'll probably lose.