The news of Wellington's momentous victory at Vitoria on 21 June 1813 reached London in early July. The celebration spawned an expectation of a rapid conclusion to events in the Peninsula. His Majesty's Government gave authority for Wellington to invade France and made noises and plans for the redeployment of the Peninsular Army in support of Russia and Prussia. Wellington, however, did not see things in quite the same way. His army was worn out and there remained sizeable French forces in Spain, so what followed had to be a carefully thought out and planned campaign.
The invasion of France is a complicated aspect of the culmination of the War in Iberia: indeed many historians consider the invasion and subsequent operations in southern France as separate from the Peninsular War as a whole. The preliminaries include Wellington's need to capture Pamplona and San Sebastian prior to the invasion and Soult's attempts to relieve both garrisons resulting in the Battle of the Pyrenees (July-August) and San Marcial (late August) respectively.
The invasion itself commenced with the daring Allied crossing of the Bidassoa estuary in early October 1813 and was followed by an operational pause prior to the Battle of Nivelle in November, another pause to re-group and the subsequent offensives on the River Nive and the Battle of St. Pierre. This phase, and ipso facto the invasion, was complete by mid December 1813. Finally, the subsequent operations, which commenced early in 1814, provided the aftermath to the invasion and the conclusion to the Peninsular War. These actions focus primarily on the investment of Bayonne and the pursuit of Soult's army east, and include the battles and engagements at Garris, Orthez, Aire, Tarbes and the final showdown at Toulouse in April 1814.