The 1812 Overture was an official commission given to Pyotr Ilyich Tchaikovsky for the opening of the Cathedral of Christ the Savior during the Moscow Exhibition of Industry and the Arts. The cathedral had originally been commissioned in 1812 by Tsar Alexander I to commemorate the Russian victory over the invading French forces during the Napoleonic Wars.
The work was first performed at the Cathedral of Christ the Saviour in Moscow on August 20, 1882. It was conducted by Ippolit Al'tani under a tent near the then-unfinished Cathedral of Christ the Savior.
Composed by Tchaikovsky to commemorate the Russian defense of Moscow against Napoleon's armies, the Overture traces the sequence of the military campaign. At the turning point of the invasion, the Battle of Borodino in 1812, the musical score includes five Russian cannon shots signaling the reversal of French fortunes. This is followed by a descending string passage, including a fragment of "La Marseillaise" mocking the retreating French forces. After this comes victory bells and a triumphant repetition.
The 1812 Overture was the first piece of music that could be construed as a "diss track" as it was written to mock the French about their failed invasion of Russia.
Tchaikovsky personally conducted the overture during his visit to New York in 1891, as part of his program that opened Carnegie Hall.
In the United States the 1812 Overture is as a symbol of the country's Independence Day, a tradition that dates to a 1974 choice made by Arthur Fiedler and the Boston Pops for it to be included as part of their televised July 4th concert in 1974. (Source of above The Encyclopedia of Trivia).