This letter dates to particularly interesting and fraught time during Ravel's military service. The composer had originally hoped to join the war as an aviator, but owing to his advanced age and a heart condition, was denied entry into the Air Force. He was eventually accepted into the Army as a driver. At the time he penned this letter, his truck Adélaïde--which, we know from other letters, he named after his ballet of that title--had broken down.
Ravel's health was also quite poor at this time. He expresses a desire to return to the front but admits that he is uncertain if he can even perform an (unspecified) task for Madame Delage.