Tinieblas translates to "darkness" or "gloom". While "darkness" is a common concept, tinieblas often carries a more profound, almost biblical or spiritual connotation than simply oscuridad.
In this song, Juan Luis Guerra uses tinieblas in a powerful, metaphorical sense, singing "Lucho en ciudades contra tinieblas y potestades" (I fight in cities against darkness and powers). It refers to spiritual or moral darkness, representing evil forces or challenges, making it a compelling and evocative word choice.
Guerra spends this whole song calling himself a soldier, but not the fighting kind. He opens flatly, almost like a statement of fact: "Soy soldado del padre y del hijo" (I am a soldier of the Father and the Son). From there every verse adds another piece of gear to the uniform: a sword that's "De doble filo" (double-edged), a breastplate made "De su justicia" (of His justice). It's the language of spiritual war set against a bright bachata guitar line, and that contrast is the whole point of the track.
By the chorus he recruits the listener too. "Y tú eres soldado" (And you are a soldier) turns a solo declaration of faith into something closer to a call and response at church. The enemy stays abstract: darkness, powers, serpents, demons, none of it literal. What's concrete is the confidence, repeated until it stops sounding like a boast and starts sounding like a habit. Grip your sword, give a war cry: "La victoria es nuestra" (the victory is ours).