Greece and Serbia have over the years developed strong ties and it is a well -known fact that in numerous cases they have constructed a sort of a Balkan entente. Important historical courses were either shaped or influenced by Greek Serbian cordial relations, such as the Balkan wars of 1912-12, WW1, WW2 and other. If it is to examine the reasons for such a long lasting common interests, one should look into the geopolitical aspect of the matter. First of all, Serbia was always a continental power, namely it lacked adequate access to the sea, whilst it was situated in a position to control the main continental corridors of the Balkan Peninsula. That is the North -South axis from the Panonian plain of Hungary-And Central Europe- to the Aegean Sea, and the West - East axis running from the Adriatic Sea towards the Black sea. Due to its geographical placement it became an arena of conflicts in periods of political and military strife, and witnessed extensive invasions as well as occupations from foreign powers that were seeking dominance in South Eastern Europe.
Greece on the other hand, is a naval power since it is affected for its coherence on the dominance of the Aegean Sea and the Ionian one. To that statement, the thousands of islands and islets should be taken into account, as well as the high importance that the mercantile navy and commerce had in this state since ancient times.
The combination therefore of continental and Sea power in the Balkans is considered to be a paragon of stability for the region since it absorbs power shifts from other interested parties and at the same time it connects in economic terms the Central European region with the Eastern Mediterranean basin and as an outcome with the Middle East. It should be noted though that this harmonious situation as described above was rarely been achieved in the past two hundred years at least.
During most of 19th century various attempts to establish common ties between those states, took place. At that period the disintegration process that already was taking place in the Ottoman Empire, culminated in an ever -expanding nationalism in smaller states like Serbia and Greece. In 1867 in Voslau the first official Greek-Serbian agreement was signed. It didnít specify any particular details as far as territorial politics were concerned but it was the first important stage for a common strategy against the Ottoman Empire. It also stated the need for further Balkan cooperation by including Bulgaria, Montenegro and possibly Romania. As year progressed the balance of powers changed in the region and Bulgaria gained a strong foothold in the wider Macedonian area, with the Saint Stefan treaty (1878), and the revisionist Berlin one (1881). That was an incentive for further initiatives for closer ties between the two discussed states and in 1885, informal negotiations were held in Belgrade where spheres of influence were drawn and Serbia for the first time requested to control a free zone in Thessalonikiís port thus recognizing indirectly Greeceís position for a claim in the city. During that period a political entity called "Saint Savvas" was formed in Belgrade under the guidance of Svetomir Nikolajevic who had strong amenity with Serbiaís royal family, and was calling for stronger relations with Greece.
The 1890ís timeline brought increasing hopes from Greeceís side for the creation of an official Athens- Belgrade axis, and for that reason the Greek Premier Trikoupis visited Belgrade in 1891, while the following year Djordjevic the Serbian one held talks in the Greek capital. The conclusions derived from those talks was that Serbia stated its interests for Southern Serbia-Currently FYROM- and proposed a common line against future claims by the Bulgarian side in those areas. Despite original Greek interest the destructive 1897 war for Greece against the Ottomans dwarfed all plans, whilst Serbians went on negotiating with the Bulgarians under Russian auspices, which at that period aspired of gaining a strong presence in the region.
A very important as well as constructive approach to the relation of the two states is their individual relations with the third interested party, in Balkan territories and that is Bulgaria. Historically when Bulgaria seemed to grow stronger Greek-Serbian relations cemented and vice versa. It is a purely power- politics attribute that can be seen in many parts of the world when there are three powers striving for local dominance. That also concludes to the Macedonian question, and that is who is going to control the whole of the historical territory (As it was in antiquity), of Macedonia. It is the most important part of the Balkans due to the fact that is a land platform that connects the Aegean sea with the inland and contains various and numerous amounts of precious metals like gold, uranium, nickel, chromium, zinc etc. Last but not least individual relations and cooperation in SE. Europe in the 19th century as in the 21st strongly and sometimes vitally, depend on the wider rivalries of larger powers that were concerned on how to solve the all timely "Eastern question", in which the Macedonia question is a parallel string and cannot be viewed by itself, as a local multiparty conflict. It would be wise to illustrate this state of affairs by paraphrasing a great historical leader; it is an enigma trapped in a wider riddle whose cords seem to trace back in the outer past.
1) Evangelos Koufos, "Dilemmas and orientations of Greek policy in Macedonia, 1878-1886".
2) Petar Milosavljevic "Greek- Serbian cooperation 1830-1908"
3) Konstantinos Vakalopoulos "Modern ethnological boundaries of Hellenism in the Balkans"
4) Evangelos Koufos "Greek-Serbian relations and the question of Macedonia, 1879-1896"
 Petar Milosavljevic "The Serbian- Greek cooperation, 1830-1908". P 83-92
 E. Kofos "Greek-Serbian relations and the question of Macedonia, 1879-1896. P 101.
 Russia, Germany, USA, UK, France, ex Austria- Hungarian Empire and Italy has all meddled in Balkan affairs military. Actually nowadays all of them-Apart from the Austrian Empire!- have troops in Kossovo, FYROM and/or Bosnia Herzegovina.
 A very illuminating description and analysis could be traced in Ioannis Loucas book "Geopolitics", Trohalia publ. Athens, 2000. Greek Ed.