On retiring, the corps was attached to the French Fifth Army during the Battle of Charleroi (21-3 August) and the Battle of Mons (23 August). By the end of 22 August, Lanrezac, commander of the Fifth Army, reported that Sordet's corps was "greatly exhausted" and that it had had to pull back, helping to open a gap of – enough for an enemy corps – between Fifth Army's left and the right of the BEF. Together with the news which reached him at noon next day that Belgian 4th Division were evacuating Namur, this helped decide Lanrezac to pull back from his position at Charleroi. Sordet telegraphed to Lanrezac at 8 pm on the 23rd that Sir John French, commander-in-chief of the BEF, was pulling back to the Bavai-Maubeuge line (in fact this was a slight misunderstanding, as he was just making inquiries about the possibility of doing so), and asked if he should "keep to [his] mission on its left". Edward Spears argued that this may have been the source for the "legend" that Lanrezac pulled back because the BEF was doing so. He wrote that in fact Lanrezac pulled back before receiving the message and answering it at 11.30pm. Barbara Tuchman disagreed, citing Lanrezac's later claim that he had "received confirmation" of Sordet's message. She also scoffed at Spears' claim that "no evidence" had been found to link Lanrezac's retreat to concern about the British retreat, observing that Messimy testified at the postwar Briey hearings that there were 25 to 30 million relevant documents for the period in the archives. Sir John French, worried at being cut off from the English Channel, visited Sordet at Avesnes on 24 August, and was informed that the Allied west flank was being defended by Territorial Army forces (reservists aged between 35 and 48) under Albert d'Amade at Arras and by the Lille garrison. Sir John asked Sordet to cover the British left, but Sordet initially asked to consult his own chain of command first. Sordet told Sir John that his horses were too tired to move, but he actually moved a long distance afterwards, a fact which Major-General Snow, commander of British 4th Division, later cited as evidence that Sordet is unlikely to have done much during the Battle of Le Cateau.