A "Last Move" problem is especially interesting if

- many last moves are completely determined, or
- the last move is tricky, or
- the problem is economical, or
- all of the above.

We count retro-moves in *single* moves, i.e. moves by one side,
so that 1. e4 e5 2. Nf3 Nc6 3. Bb5 is **5 single moves**.
(The "half-move" terminology has other meanings).

We say a (single retro-) move is *completely determined* if
we know the exact from- and to- squares and which enemy unit was captured
(if any). That is, when we know exactly how the board was before this
last move. Usually, problems asking for "last *n* singles moves"
ask for completely determined moves.

A recent record-breaking problem by P. Wassong and G. Wilts has 55 last single moves completely determined !

**Pascal Wassong (version by Gerd Wilts)**

Dedicated to Babette

14+12. Last 55 single moves?

- Type A: It is not given who has the move. Neither king is in check.
- Type B: The stipulation says who has the move. Neither king is in check.
- Type C: It is not given who has the move. A King is in check.
- Type D = duplex Type B: One solution assuming White has the move, another one solution assuming Black has the move (not covered here)

Obviously, the choice of potentially possible last moves is larger in Type A problems than in Type B, and in Type B than in Type C. That is why Type A problems are usually preferred.

Here is an example that everybody has already seen. It is a Type B with only one precisely determined last move (reader's exercise: why not the last two single moves?)

**J. Mortensen**

1956

3+1. What did White just play?

As an example, here is the (so far) most economical presentation of KxN in Type A (to compare with the problem we just saw and which happens to be the most economical KxN in Type B.)

**Hugo August**, **Otto Brennert**,
**Thomas R. Dawson**, **Niels Høeg** and
**Valerian Onitiu**

Skakbladet, 1924

4+3. Last move?