You are correct with that assumption:
Keep in mind that just by reading the card you should be able to realize that though.
Mystic Swordsman LV4
Effect Monster (Warrior / EARTH / 4 Stars / ATK 1900 / DEF 1600)
If you Normal Summon this card, you must place it in face-down Defense Position. If this card attacks a face-down Defense Position monster, destroy the monster immediately with this card's effect without flipping it face-up or applying damage calculation. During the End Phase of a turn that this card destroyed a monster as a result of battle, send this card to the Graveyard to Special Summon 1 "Mystic Swordsman LV6" from your hand or Deck.
The word "must" tells you there is no other way.
But if you didn't realize that... here is the official ruling on RONIN (and then that means it's on UDE's FAQ pages and our own here at netrep.net).
"¢ If "Light of Intervention" is active, you cannot Normal Summon "Mystic Swordsman LV4" because it can only be Normal Summoned face-down, which "Light of Intervention" makes impossible to do.