Decode this message received by Space Defence Control

Question

The following is in my A level textbook categorised as an 'easy' question:

Decode this message received by Space Defence Control. MKW PWCCFQ USFGWJOWWM LU FSSARFGKLQC SOWFUW UWQH KWOS XW QWWH PRAW CFOFGMLG ABQFDRBMU XLMK KLCK USWWH OFUWA CBQU

I've looked at so many different variables, such as how often letters occur, and what these numbers correspond to in the alphabet, but I just cannot get anywhere.

I fail to see how this is 'easy' or even mathematical, as the person who encoded it could've chosen any method they wanted to, and so getting the right one is just guessing and trial and error.

What am I missing here?

Answer 1

user296602 has the right idea. I have not found a pattern in the cipher so you have to figure out one letter at a time. After making a few educated guesses it basically becomes a game of Wheel of Fortune. The message reads:

The Meggan spacefleet is approaching please send help we need more galactic runabouts with high speed laser guns

Answer 2

It is a substitution cipher where the ciphertext is given by the bijection $$\begin{matrix} a&b&c&d&e&f&g&h&i&j&k&l&m \\ F&D&G&H&W&J&C&K&L&E&Z&O&P\\ n&o&p&q&r&s&t&u&v&w&x&y&z\\ Q&R&S&I&A&U&M&B&V&X&T&Y&N \end{matrix}$$ Given the encoded message:

MKW PWCCFQ USFGWJOWWM LU FSSARFGKLQC SOWFUW UWQH KWOS XW QWWH PRAW CFOFGMLG ABQFDRBMU XLMK KLCK USWWH OFUWA CBQU

then the decoded message is:

the meggan spacefleet is approaching please send help we need more galactic runabouts with high speed laser guns

P.S. I found an online Substitution Solver which is able to decipher this "english" message automatically!!!