In 1581, Ivan the Terrible annexed the Khanate of Sibir and commenced Russia’s eastward expansion to the Pacific Ocean, which was reached a century later in 1679. Then Peter the Great expanded west to the Baltic Sea by conquering Ingria from Sweden in 1702. Russia had gained its national territory stretching from sea to sea (Baltic to Pacific).
The process was repeated by the United States of America. In 1845, it espoused the concept of its “Manifest Destiny” to expand eastward to the Pacific Ocean. The following year it achieved this by annexing Oregon. This was celebrated by the phrase “From sea to shining sea” (ie Atlantic to Pacific) in the patriotic song America The Beautiful.
Canada followed suit annexing British Columbia in 1871 and thereby emulating its southern neighbour the USA by gaining a national territory stretching right across the continent. To celebrate this it adopted the title of Dominion of Canada with the national motto A Mari Usque Ad Mare (From Sea to Sea), taken from Psalm 72 verse 8 : “He (ie God) shall have dominion from sea to sea.”
In 1901, the self-governing British colonies in Australia federated to achieve unity of the island continent. These countries had coastlines as desired limits to national territory. Italian nationalists had the Alps as their goal. In 1861, they established the Kingdom of Italy consisting of most of the Italian peninsula. In 1878, the Irredentist Party was founded there, dedicated to annexing Italia Irredentia (Unredeemed Italy) ie territory south of the Alps under foreign rule. Pursuing a policy of “Sacred Egotism”, Italy entered the First World War to achieve this. As a result, Istria and South Tyrol; were gained from Austria in 1919, thereby giving Italy the desired Alpine frontier.
In 1815, the pre-Napoleonic frontiers of France were restored by the Congress of Vienna. France thereby occupied the symmetrical hexagon of territory achieved by the Sun King Louis XIV in 1697 when he annexed North Alsace. This was the accepted national heartland as accepted by King Louis XV in the 1748. Thus the German annexation of Alsace-Lorraine in 1871 was regarded as illegal encroachment. French maps thereupon showed the lost territory in black and all her politicians pledged to regain it. The issue became one of the main causes of the First World War, which resulted in France regaining the lost lands in 1918. “Le Hexagon”, as it is called in France, was re-established as the national territory ( illustrated in the trademark of Delice de France).
Other countries have similar irredentist claims. Having lost the Pacific War in 1883, Bolivia was deprived of its coastline (Arica) to become landlocked. This has remained unaccepted and, ever since, each Bolivian government has pledged to regain Arica (from Chile) as the national port. There is an annual day dedicated to this cause. Similarly in 1955, landlocked Afghanistan claimed Pakhtunistan (Land of the Pathans) from Pakistan to unite its main tribe and achieve a coastline, with a designated anniversary dedicated to this. In 1960, Togo and Somalia achieved independence Each thereupon claimed what it believed was its rightful national territory. Togo claimed Western Togoland (which the British had made part of Ghana) to achieve unity of the Ewe people. Similarly Somalia claimed Djibouti, North-East Kenya and Ogaden (from Ethiopia) to achieve unity of the Somali people.
Each country has a definition of its national territory which it will strive to achieve or maintain. Irish nationalists will thus never accept the loss of Northern Ireland brought about by the partition of 1922.