Boyer was chief of staff in Jean-Andoche Junot's VIII Corps during Marshal André Masséna's invasion of Portugal in 1810. The VIII Corps was held in reserve at the Battle of Bussaco but was involved in a skirmish with the British in the Battle of Sobral on 13–14 October 1810.
1814
On 19 January 1814, Marshal Jean-de-Dieu Soult received the order to begin the transfer of the infantry divisions of Boyer and Jean François Leval to Napoleon's army operating near Paris. They began their march on 21 January. Boyer's division left behind Jean-Baptiste Pierre Menne's brigade, the 118th and 120th Line Infantry Regiments, and instead took David Hendrik Chassé's brigade, the 16th Light, 8th Line and 28th Line. Boyer received promotion to general of division on 16 February 1814. A detachment under Étienne Gauthier arrived in time to join Marshal Nicolas Oudinot's corps for the Battle of Mormant on 17 February. Present were two battalions each of the 2nd Light and 122nd Line and one battalion each of the 24th Line and 33rd Line. The 33rd was a new unit of conscripts that joined along the way. On 22 February, Antoine Gruyer led 3,600 men of the 2nd Light, 24th Line, 36th Line and 122nd Line plus the 6th Chevau-léger Lancers in an attack on Méry-sur-Seine. There were 5,000 Russians and 1,200 Prussians in opposition. Both sides suffered about 800 casualties including Gruyer wounded. Chassé's 2nd Brigade, which was made up of the 16th Light, 8th Line, 28th and 54th Line, was not engaged. In the action, the French overran the village of Méry, but were unable to hold the part of the town on the north bank in the face of an Allied counterattack. Boyer later reported that the army of Gebhard Leberecht von Blücher was moving west along the Seine River. This alerted Napoleon that the Prussian general might be trying to cut his communications with Paris. On 27 February, Napoleon followed Blucher's army which had moved northwest toward Meaux. At this time, Gruyer's brigade, under Boyer, was attached to Napoleon's army. Boyer's other brigade was left in the south with the army of Marshal Jacques MacDonald. Boyer's brigade was involved in a skirmish with Russian forces on 6 March. The next day during the Battle of Craonne, Boyer's brigade operated with Marshal Michel Ney's Young Guard corps. That morning Ney prematurely launched the divisions of Boyer and Claude Marie Meunier against the Russian left flank. Because Ney failed to provide artillery support, the initial attacks failed. When the French guns arrived, Meunier and Boyer's troops fought a costly battle with their enemies for several hours. At 2:30 pm, Boyer's men finally captured the village of Ailles on the extreme French right flank. For the rest of the day, Boyer followed up the Russian withdrawal.