I dodged, but the blow was a feint.
or
I dodged but the blow was a feint.
***** NOT A TEACHER *****
Good afternoon, Placidran.
(1) You have two sentences:
I dodged.
The blow was a feint.
(2) Of course, you do not usually want to speak or write that way
(although it is, of course, "perfect " English).
(3) If you want to combine them for one "smooth" sentence, you
need a connecting word usually called a conjunction.
(a) "but" is a conjunction.
(4) If you are connecting two sentences, you usually need a comma in
front of "but":
I dodged, but the the blow was a feint.
Have a nice day!