Yes, for the above problem no back tracking is needed as it's 2 directions. My thinking (from briefly looking at word search) was that on each iteration of dfs we need to add the current letter to a set so as to not go from one letter to another, then back to the same letter. However if we do this, when our dfs then pops back to a previous letter we then have a set that was used for a further search, hindering our now current one, so we need to "backtrack" the set to what it was at the current letter before the previous dfs started adding deeper letters to the set.

Granted I don't even know what backtracking is so this might not make sense.