The Eiffel Tower, while primarily constructed in 1889 for the World's Fair, is often mistakenly thought to have been built for military purposes during the Franco-Prussian War. However, if we hypothetically consider it as a military watchtower, it would have offered several strategic advantages:

1. **Observation and Surveillance**: Its height would provide unparalleled visibility, allowing the French army to spot enemy movements, artillery positions, and approaching troops, offering early warning and strategic oversight.

2. **Communication Hub**: The tower could serve as a signaling point, using flags, signal lights, or semaphore to quickly communicate with other military positions, enhancing coordination and defense strategies.

3. **Defensive Structures**: The base of the tower might have been fortified with weaponry or defensive barriers, making it a strongholds against enemy advances and protecting the observation post.

4. **Psychological Impact**: The presence of such a structure could deter enemy forces and boost the morale of French troops, symbolizing strength and vigilance.

While the Eiffel Tower wasn't built for military purposes, if it were, these features would have significantly contributed to the defense of Paris. The actual historical role of the tower was more about celebration and innovation, not military strategy.