殉 means 'to die for / to follow into death' — appears in a series of solemn compounds:
殉国 (xùnguó) 'die for one's country',
殉职 (xùnzhí) 'die in the line of duty',
殉情 (xùnqíng) 'die for love (suicide pact)',
殉道 (xùndào) 'die for one's faith / a martyr'.
殉难 is the broadest, covering deaths in wartime, disasters, persecutions, and resistance.