Limitrophe states:

1. historically — from , provinces at the borders of the Roman Empire
   Borders of the Roman Empire
   The borders of the Roman Empire, which fluctuated throughout the empire's history, were a combination of natural frontiers and man-made fortifications which separated the lands of the empire from the "barbarian" countries beyond.-The Limes:A limes was a border fortification system of the Roman...
   
   , which were obliged to provide billeting of the limitanei
   Limitanei
   The limitanei, meaning "the soldiers in frontier districts" The limitanei, meaning "the soldiers in frontier districts" The limitanei, meaning "the soldiers in frontier districts" (from the Latin phrase limes, denoting the military districts of the frontier provinces established in the late third...
   
   legion
   Roman legion
   A Roman legion normally indicates the basic ancient Roman army unit recruited specifically from Roman citizens. The organization of legions varied greatly over time but they were typically composed of perhaps 5,000 soldiers, divided into maniples and later into "cohorts"...
   
   s deployed on their territory, mostly in limes
   Limes
   A limes was a border defense or delimiting system of Ancient Rome. It marked the boundaries of the Roman Empire.The Latin noun limes had a number of different meanings: a path or balk delimiting fields, a boundary line or marker, any road or path, any channel, such as a stream channel, or any...
   
   .
2. in the broader sense (from diplomatic
   Diplomacy
   Diplomacy is the art and practice of conducting negotiations between representatives of groups or states...
   
    French
   French language
   French is a Romance language spoken as a first language in France, the Romandy region in Switzerland, Wallonia and Brussels in Belgium, Monaco, the regions of Quebec and Acadia in Canada, and by various communities elsewhere. Second-language speakers of French are distributed throughout many parts...
   
    "pays limitrophes", border countries) — any group of neighbours of a given nation which border to each other thus making a rim around this country.
3. in modern history — provinces which seceded from the Russian empire
   Russian Empire
   The Russian Empire was a state that existed from 1721 until the Russian Revolution of 1917. It was the successor to the Tsardom of Russia and the predecessor of the Soviet Union...
   
    at the end of World War I
   World War I
   World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...
   
   , during the Civil War in Russia (1918–1922), thus forming a kind of belt separating the Soviet Russia
   Soviet Russia
   Soviet Russia usually refers to the Russian Soviet Federative Socialist Republic, one of the fifteen republics of the Soviet Union. It may also denote:* Soviet Russia , magazine of the Friends of Soviet Russia in the United States...
   
    from the Western powers.

1918–1939

Before the Treaty of Versailles

Treaty of Versailles

The Treaty of Versailles was one of the peace treaties at the end of World War I. It ended the state of war between Germany and the Allied Powers. It was signed on 28 June 1919, exactly five years after the assassination of Archduke Franz Ferdinand. The other Central Powers on the German side of...

 was signed on and even after it was not clear yet, which territories of Russian Empire

Russian Empire

The Russian Empire was a state that existed from 1721 until the Russian Revolution of 1917. It was the successor to the Tsardom of Russia and the predecessor of the Soviet Union...

, either occupied by German troops or engaged in the Civil War in Russia, may maintain their independencies which they started to proclaim from late 1917. Thus the very composition of the Limitrophe zone was uncertain and varied widely. Arguing that these nations were then "the cards to change hands in big political games", authors name among them the Baltic peoples, Poles,
Lithuanians, Ukrainians, Byelorussians and so on.

The usage of term "limitrophe states" continued after the World War I treaties were signed through the beginning of the World War II

World War II

World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

. The Small Soviet Encyclopedia

Small Soviet Encyclopedia

The Small Soviet Encyclopedia was a general encyclopedia published in the Soviet Union. The encyclopedia was published in three editions:...

 (1929) defines the limitrophe states as "states formed from the outskirts of the former Tsarist Russia, mainly from the western provinces". It includes in their list Estonia

Estonia

Estonia , officially the Republic of Estonia , is a state in the Baltic region of Northern Europe. It is bordered to the north by the Gulf of Finland, to the west by the Baltic Sea, to the south by Latvia , and to the east by Lake Peipsi and the Russian Federation . Across the Baltic Sea lies...

, Latvia

Latvia

Latvia , officially the Republic of Latvia , is a country in the Baltic region of Northern Europe. It is bordered to the north by Estonia , to the south by Lithuania , to the east by the Russian Federation , to the southeast by Belarus and shares maritime borders to the west with Sweden...

 and Lithuania

Lithuania

Lithuania , officially the Republic of Lithuania is a country in Northern Europe, the biggest of the three Baltic states. It is situated along the southeastern shore of the Baltic Sea, whereby to the west lie Sweden and Denmark...

, adding "and, partially, Poland

Poland

Poland , officially the Republic of Poland , is a country in Central Europe bordered by Germany to the west; the Czech Republic and Slovakia to the south; Ukraine, Belarus and Lithuania to the east; and the Baltic Sea and Kaliningrad Oblast, a Russian exclave, to the north...

 and Finland

Finland

Finland , officially the Republic of Finland, is a Nordic country situated in the Fennoscandian region of Northern Europe. It is bordered by Sweden in the west, Norway in the north and Russia in the east, while Estonia lies to its south across the Gulf of Finland.Around 5.4 million people reside...

". Nine years later the Ushakov's Explanatory Dictionary (1938) also syntaxically 'separates' Finland fron the three Baltic States

Baltic states

The term Baltic states refers to the Baltic territories which gained independence from the Russian Empire in the wake of World War I: primarily the contiguous trio of Estonia, Latvia, Lithuania ; Finland also fell within the scope of the term after initially gaining independence in the 1920s.The...

: ("Estonia, Lithuania, Latvia and Finland as well"), however Poland is not mentioned in this list.

The Directive "On the preparation of Wehrmacht

Wehrmacht

The Wehrmacht – from , to defend and , the might/power) were the unified armed forces of Nazi Germany from 1935 to 1945. It consisted of the Heer , the Kriegsmarine and the Luftwaffe .-Origin and use of the term:...

 for 1939-1940" signed on by Adolf Hitler

Adolf Hitler

Adolf Hitler was an Austrian-born German politician and the leader of the National Socialist German Workers Party , commonly referred to as the Nazi Party). He was Chancellor of Germany from 1933 to 1945, and head of state from 1934 to 1945...

 said, in particular, that: