Final answer:
José Martí was concerned about American intervention possibly leading to U.S. control over an independent Cuba, which is what he sought to prevent by advocating for Cuban self-governance.
Step-by-step explanation:
José Martí was very concerned about the possibility of American military intervention in Cuba because he feared that it would lead to the United States controlling Cuba after its independence from Spain. Martí's concerns were not unfounded, as following the Spanish-American War, the U.S. did indeed exert significant influence over Cuban affairs, most notably through the Platt Amendment which allowed for U.S. intervention in Cuban internal affairs. This outcome was precisely what Martí aimed to avoid; he wanted Cuba to be free and independent, not simply transferred from Spanish domination to American influence.