Complex sentence: By 26 July Petain had supplied four more divisions and on 31 July XXXVI Corps, already deployed behind First Army, was put under Debeney's command, although it remained in reserve.
Split into simpler sentences: By 26 July Petain had supplied four more divisions. Doughty 2009, p476-9 On 31 July XXXVI Corps, already deployed behind First Army, was put under Debeney's command, although it remained in reserve.