Who believed force should be used to preserve the union

Abraham Lincoln.

Explanation:

Abraham Lincoln was President of the United States from 1861 to 1865. Prior to his political career, he worked as a ferry, general merchant and post office manager, among others. Unlike previous presidents, he was a congressman for only one term. Even in the army, he served only a short time as a volunteer and was a mere soldier of military rank.

Lincoln had no intention of abolishing slavery, but of limiting it territorially and gradually, but this was seen as a threat in the south of the country. Shortly after taking office, the southern pro-slavery states seceded from the Union and formed the Confederation, and the United States plunged into civil war. In view of this situation, Lincoln saw the use of force as the only suitable means to maintain the union of the country, and avoid the effective secession of the Confederacy.

Finally, Lincoln managed to win the Civil War and unite the country. He greatly influenced the subsequent status of the black population in the United States and is widely regarded as one of the best presidents in the country.