Short answers, pulled from the story.
The Grande Armée was the primary field army of the French Imperial Army during the Napoleonic Wars, commanded by Napoleon. It was formally constituted in 1804 from the Armée des côtes de l'Océan, a force originally assembled at Boulogne for a planned invasion of Britain. From 1804 to 1812, it won a series of military victories that gave the First French Empire control over most of Europe.
The Grande Armée reached its peak strength at the start of the Russian campaign in June 1812, with a total invasion force of 685,000 men drawn from across Europe. This included 410,000 from the French Empire, 95,000 Poles, 35,000 Austrians, 30,000 Italians, and smaller contingents from Bavaria, Saxony, Prussia, Switzerland, Denmark, Norway, Spain, Portugal, Croatia, and Ireland.
Of the 685,000 men who crossed the Niemen River on the 24th of June 1812, only 93,000 survived the campaign. As many as 380,000 died from battle, disease (principally typhus), starvation, cold, and Cossack raids. Of those who escaped, only 35,000 were French; the survivors were predominantly Austrians, Prussians, other Germans, and Poles.
Each corps of the Grande Armée was a self-contained combined-arms force of 10,000 to 50,000 men, capable of independent operations and of defending itself until reinforced. Corps marched on separate routes to live by foraging, reducing supply needs, while staying within a day's marching distance of one another. This flexibility allowed the army to concentrate rapidly and surprise opponents with its speed of maneuver.
To join the Old Guard Foot Grenadiers, a recruit had to have served at least 10 years, received a citation for bravery, be literate, and stand over 178 centimetres tall. Some veterans of the regiment had served in more than 20 campaigns. Napoleon gave the Grenadiers the nickname Les Grognards, The Grumblers, during the 1807 campaign in Poland.
The Grande Armée ended with a total defeat during the Hundred Days in 1815. Napoleon returned from exile on Elba in February 1815 and launched the Waterloo campaign beginning on the 15th of June. A victory over the Prussians at the Battle of Ligny on the 16th of June was offset when Marshal Grouchy's delayed pursuit allowed Blücher to march to Wellington's aid at Waterloo, resulting in Napoleon's final defeat. The Treaty of Paris in 1815 concluded the Napoleonic Wars.