Synonyms for Deserter (same or very similar meaning)
WordNet sense 1 (a disloyal person who betrays or deserts his cause or religion or political party or friend etc.):
apostate, ratter, recreant, renegade, turncoatWordNet sense 2 (a person who abandons their duty (as on a military post)):
defectorFrom the ODE community, based on WordNetadd/edit