Contrary to popular assumptions, the Austro-Hungarian Empire was still growing in 1918.
|Dark Purple Area Ceded to Austria-Hungary by Romania|
The last territorial change within the Austro-Hungarian Dual Monarchy took place in the last year of the First World War. In May 1918, the Dual Monarchy signed a peace treaty with Romania in Bucharest. As a result, an area of 5,636 km was annexed to the empire (a strip with a width of 3–16 square kilometers at the eastern and southern feet of the Carpathian Mountains and at the eastern border of Bukovina). These territorial changes can be explained by the intention of providing improved conditions for guarding the empire’s borders. By annexing Bosnia and Herzegovina, the empire’s very long borders originally running through Croatia, Slavonia and Dalmatia got considerably—by hundreds of kilometers—shortened. The terms of the Peace Treaty of Bucharest also included the establishment of a better defense system in the Carpathian region.
Source: "Was Austria-Hungary a Great Power," Mihály Miklós NAGY – László GULYÁS