WWI

First off, don't invade Belgium

second off, send among us armor men to take the line.

Alright

We need to try and find away to prevent diseases on the eastern front so we can advance further into Russia

Simple
We give our men adequate cold-weather gear and face masks, as well as gloves. we also demand soldiers have injections to combat illness if they do attract it.
*combat results: Few germans got seriously ill during the eastern theatre. this is not the case for russia, and the Tsar abdicates after an embarassing defeat at Tsaritsyn. the left-wing provisional government led by lenin sues for peace by early 1915.*
Now we just need to figure out a counter to trench warfare deployed by the British and the French.

Well I try to shuttle as many pieces of artillery over there as fast as possible to start heavier shelling

Don't forget tanks and mobile warfare