Shell Programming and Scripting

I have many files similar to this one: AC41_AC85_86_AC128_129_MC171_173_SF_207_FMV.pdf.

I want a directory named AC41 and to put the file AC41_AC85_86_AC128_129_MC171_173_SF_207_FMV.pdf into the directory. Next, a directory named AC85 and put the file into it. Also, continue to cycle through this pdf and all pdfs in the folder.

I have a script:

#!/bin/sh

set -e
for f in *.pdf
do
d=${f%_*.*}
if [ ! -d "$d" ]; then
mkdir "$d"
fi
mv -f "$f" "$d"
done

This only creates one directory per file. What am I missing?

Double post, continued here, thread closed.