So, kind of old thread, and this isn't an definitive answer, but a clue, i have a snippet old old source code from the game and here is the only part where the DMOH might get awarded:
Code:
if (nScoreMax >= 200) // High-difficulty missions
{
if (m_aAwards[AWARD_SILVER_STAR] == 0)
IssueAward(AWARD_SILVER_STAR);
else if (rPercent >= 0.99f && m_aAwards[AWARD_NAVY_CROSS] != 0)
IssueAward( AWARD_MEDAL_OF_HONOR );
else
{
if (rPercent >= 0.9f)
IssueAward( AWARD_NAVY_CROSS );
else
IssueAward( AWARD_SILVER_STAR );
}
}
So in other words, you'd have to be in a difficult mission anyway (over 200 points total), and have already received both the silver star and navy cross in previous missions. And play at 100% difficulty.
I can't guarantee there isn't a bug somewhere preventing the DMOH anyway, even if not, this could lead to bonkers situations where you have to singlehandedly sink the Scharnhorst or Yamato multiple times to get enough medals.