Beginning with the plaintive Slavic Orthodox Troparion of the Holy Cross played by four cellos and two violas, the piece moves through a mixture of pastoral and martial themes portraying the increasing distress of the Russian people at the hands of the invading French. This passage includes a Russian folk dance, At the Gate, at my Gate (U Vorot, Vorot"). At the turning point of the invasion—the Battle of Borodino—the score calls for five Russian cannon shots confronting a boastfully repetitive fragment of La Marseillaise. A descending string passage represents the subsequent retreat of the French forces, followed by victory bells and a triumphant repetition of God Preserve Thy People as Moscow burns to deny winter quarters to the French. A musical chase scene appears, out of which emerges the anthem God Save the Tsar! thundering with eleven more precisely scored shots. The overture utilizes counterpoint to reinforce the appearance of the leitmotif that represents the Russian forces throughout the piece. A total of sixteen cannon shots are written into the score of the Overture.http://en.wikipedia.org/wiki/1812_Overture#Musical_structure
The music can be interpreted as a fairly literal depiction of the campaign: in June 1812, the previously undefeated French Allied Army of over half a million battle-hardened soldiers and almost 1,200 state-of-the-art guns (cannons, artillery pieces) crossed the Niemen River into Lithuania on its way to Moscow. The Russian Orthodox Patriarch of All the Russias, aware that the Russian Imperial Army could field a force only a fraction of this size, inexperienced and poorly equipped, called on the people to pray for deliverance and peace. The Russian people responded en masse, gathering in churches all across the Empire and offering their heartfelt prayers for divine intervention (the opening hymn). Next we hear the ominous notes of approaching conflict and preparation for battle with a hint of desperation but great enthusiasm, followed by the distant strains of La Marseillaise, the French National Anthem, as the French approach. Skirmishes follow, and the battle goes back and forth, but the French continue to advance and La Marseillaise becomes more prominent and victorious – almost invincible. The Tsar desperately appeals to the spirit of the Russian people in an eloquent plea to come forward and defend the Rodina (Motherland). As the people in their villages consider his impassioned plea, we hear traditional Russian folk music. La Marseillaise returns in force with great sounds of battle as the French approach Moscow. The Russian people now begin to stream out of their villages and towns toward Moscow to the increasing strains of folk music and, as they gather together, there is even a hint of celebration. Now, La Marseillaise is heard in counterpoint to the folk music as the great armies clash on the plains west of Moscow, and Moscow burns. Just at the moment that Moscow is occupied and all seems hopeless, the hymn which opens the piece is heard again as God intervenes, bringing an unprecedented deep freeze with which the French cannot contend (one can hear the winter winds blowing in the music). The French attempt to retreat, but their guns, stuck in the freezing ground, are captured by the Russians and turned against them. Finally, the guns are fired in celebration and church bells all across the land peal in grateful honor of their deliverance from their "treacherous and cruel enemies."
"True patriotism sometimes requires of men to act exactly contrary, at one period, to that which it does at another, and the motive which impels them — the desire to do right — is precisely the same."
- Robert E. Lee