Russell Kelly was born on June 13, 1891 in Long Island, NY. He was MIA and presumed dead on June 16, 1915 during the Battle of Artois.
RUSSELL KELLY of New York was a cadet at the Virginia Military Institute. Both abandoned their studies to join the Legion and were placed in the so-called American squad. John Earl Fike, known to the Legion as "John Smith", was still another member of the squad; his previous career had included gold-seeking in Alaska, soldiering in the Mexican and Chilean revolutions, and also serving in the United States army at home and in the Philippines. All these three were reported missing immediately after the Souchez affair on June 16 and 17, 1915; Scanlan, after lying wounded for fifty-six hours on the battlefield, was rescued by a stretcher-bearer, but Fike and KELLY were never to be heard from.
~~ Alice S. Weeks, Greater Love Hath No Man (Boston: Bruce, Humprhies, Inc., 1939).
From the Mémoire des homes (French Ministry of Defense) Website:
Russel KELLY
Mort pour la France le 16-06-1915 (Souchez, 62 - Pas-de-Calais, France)
Né(e) le/en 13-06-1893 à New-York (Etats-Unis) 22 ans, 0 mois et 3 jours
Career:
Rank: soldat de 2e classe
Unit2e régiment de marche du 1er régiment étranger (2e RM du 1er RE)
Class: 1914 (EV)
Recruitment office: Bordeaux (33)
Recruitment roll number: 997
Reference: Mort pour la France
Place of transcription of death: Souchez (62 - Pas-de-Calais, France)

A Book or Russell Kelly's service provides more information on his service:
Title: Kelly of the Foreign Legion Letters of Légionnaire Russell A. Kelly
Author: Russell A. Kelly
Editor: James Edward Kelly
Extract form this book:CHRONOLOGICAL MILITARY RECORD OF RUSSELL A. KELLY 1914
November 3, left New York on steamship Orcadian.
November 19, reached Pauillac, France.
November 21, Saturday, docked at Bordeaux.
November 23, applied at recruiting station.
November 24, enlisted in the Foreign Legion.
November 26, began military training at Dépôt de Lyon.
1915
February 6, left barracks for the front.
February 8, arrived at Bouzy, near the front.
March 8, left Bouzy and same day arrived at Verzenay and entered first line trenches.
April 24, left Verzenay for region north of Arras.
April 28, reached Aubigny; again entered first line trenches.
May 9, Sunday, in the attack on La Targette and Neuville St. Vaast.
May 10, battle continued.
May 11, relieved from the captured position and returned with regiment to rear for reorganization.
May 29, reëntered first line trenches.
June 16, in the attack on Cabaret Rouge near Souchez and at the taking of Hill No. 119.
June 18, reported as missing.
1917
May Still missing.
Is this military record, like the record of many another Legionary, forever closed; and does that youthful
“Heart that once beat high for praise Now feel that pulse no more?”