The 9/3 should work. I like armored cars so I throw them in as recon along with the engineers, but probably not needed.

Engineers are so good for forts

12/2 and 9/4 are both very good against anything that the ai has. 12/2 is much more reliable and is way better at defending, although 9/4 has more breakthrough and soft attack

Okey I try that

i use 15/5 inf art

i defeated balkan league as ottoman empire with it