 Complete the following phrase:  In 1807 Margaron was assigned to the 1st Corps of Observation of the Gironde under Jean-Andoche Junot. Margaron and Antoine Maurin led brigades in the 1,754-man cavalry division under François Étienne de Kellermann. The mounted troops included one squadron each from the 1st, 3rd, 4th, 5th, 9th and 15th Dragoon and 26th Chasseurs à Cheval Regiments. All squadrons counted between 236 and 262 troopers. With Spains permission, Junots force crossed the Bidasoa River on 18 October 1807 and was in Salamanca by 12 November, prepared to invade Portugal. Little did the Spanish know that Napoleon soon planned to overthrow their kingdom as well. Soon after Junots corps launched the 