Desperate to keep the tower going, in 1908 they figured out that the metal monstrosity had a radio antenna range of 6,000 km (3,728 miles). A distance so great it can pick up signals all the way to China.

The tower was granted a life extension in 1910, and it gets equipped with new radio capabilities. 4 years later in 1914, the tower is catching and decoding German war messages.

https://www.snexplores.org/article/how-science-saved-eiffel-tower

On the verge of losing a broken Paris to imminent German invasion, the tower heard transmissions about the Germans having difficulty and delaying their attack. The French used this knowledge to stop retreating and instead start an immediate counter offensive. They saved Paris and turned the tide of the war, in a battle known as the Miracle of the Marne.