Serbia

Serbia (1882-1918) is a (★) Balkan nation with a hard difficulty that is typically a doorstep for Austria-Hungary and Bulgaria.

A.D 1914
Serbia begins in the Balkans immediately in danger. They border Austria-Hungary, Montenegro, Greece, Bulgaria and Romania. Their allies are the United Kingdom, France, the Russian Empire, Italy, Belgium, Portugal, Greece, Montenegro, and Romania. What puts Serbia in a bad place is that Bulgaria has 3 generals waiting to kill them and either Greece or Romania. Not to mention that Austria-Hungary has troops near it. The Serbian generals include Stepa Stepanovic (Cavalry) and Radomir Putnik (Artillery)

Strategy:
No strategy has been found yet, suggest in the comments.

A.D 1917
Serbia is significantly smaller and more cramped and loses its border with Greece but gains one with the Ottoman Empire. Their new allies include the United States, Peru, Brazil, Morocco and Libya. Their new generals are Živojin Mišić (Infantry) and Stepa Stepanovic (Cavalry) The Austro-Hungarians can easily bombard you with their artillery and they have a general relatively near. Bulgaria still poses a threat but not as much as in 1914 since your allies will help you out as the Balkan nations are more centralised.

Strategy:
No strategy has been found yet, suggest in the comments.