A letter from Julius Caesar

Julius_Henke  -  October 17, 2019

Last night I managed to 🤺 ambush a courier who was carrying an important ✉️ letter. It is signed by Gaius Julius Caesar himself.
I don’t understand it’s content, but I am pretty sure his army is planning to ⚔️ attack somewhere.

Here is the letter:

Ikxitkx yhk utmmex.
Hnk xgxfr bl ytk lnixkbhk bg gnfuxkl. Rxm B dghp ahp px vtg ybgteer wxyxtm max Ztnel.
Px pbee lnkkhngw maxbk vtfi tgw lmtkox maxf mh wxtma.
Lbgvx maxr tkx hg t abee uxmpxxg mph kboxkl, px atox mh unbew t lbxzx kbgz. Mabl kbgz lahnew bgvenwx uhma hnmxk utgdl.
Oxkvbgzxmhkbq pbee lhhg ux wxyxtmxw.
G. I. Caesar

Can you help me find out which 🗺️ location they want to attack?