As a sickened person living in the USA, President Trump has made himself my enemy through mistreatment of the poor, sick and elderly.

The greatest enemy of USA citizens is their own government.

Your enemy is not in the Middle East or Asia, it is your own government.

Truth is the greatest enemy of professional astronomy.

Mal-acclimatization to very high altitudes is the enemy of mental and physical health in the sea level adapted human.