The Servians, who before the second Balkan war would have been satisfied with the Vardar river as a boundary, now insisted upon the possession of the important towns of Kotchana, Ishtib, Radovishta, and Strumnitza, to the east of the Vardar.

Serbia, shut out from the Adriatic, had no alternative save to seek her economic outlet down the valley of the Vardar towards the Aegean, and in so doing she came into violent conflict with Bulgarian aspirations in Macedonia.

The action of Austria-Hungary in vetoing her access to the Adriatic forced Serbia to turn her eyes from west to south and to seek her economic outlet to the sea down the valley of the Vardar to Salonica and the Aegean.

The cession of Monastir, Ochrida, and the Vardar Valley to Bulgaria would have rendered this impossible, for it would not merely have driven a wedge between Serbia and Greece, but would have placed two customs frontiers, the Bulgarian and the Greek, between Serbia and the sea, instead of only one, the Turkish, as hitherto.

Every fresh intrigue of Sofia with Vienna confirmed Belgrade in its view of the vital necessity for retaining the Vardar Valley.

Already no doubt they were both gratified that the spheres of their military occupation were conterminous and that no Turkish territory remained for Bulgaria to occupy west of the Vardar River.

Macedonia to the west of the Vardar and Bregalnitza Rivers was the only part of Turkey which adjoined Greece and Servia.

Already her victorious armies had occupied Macedonia from the Albanian frontier eastward beyond the Vardar River to Strumnitza, Istib, and Kochana, and southward below Monastir and Ghevgheli, where they touched the boundary of the Greek occupation of Southern Macedonia.

Why then was Bulgaria so insistent on getting beyond that base line, crossing the Vardar, and possessing herself of Central Macedonia up to Ochrida and the eastern frontier of Albania?

Meanwhile the Servian and Greek forces were fighting the Bulgarians hard at Kilkis, Doiran, and other points between the Vardar and the Struma.

At the mouth of the Vardar the fresh-water fowls were starting up with noisy cries, or standing on the edge of the bank immovable upon their long legs.

In the earlier historical times the whole of the eastern part of the Balkan peninsula between the Danube and the Aegean was known as Thracia, while the western part (north of the forty-first degree of latitude) was termed Illyricum; the lower basin of the river Vardar (the classical Axius) was called Macedonia.

The importance of this point was greatly emphasized by the existence of the Nish-Salonika railway, which is Serbia's only direct outlet to the sea, and runs through Macedonia from north to south, following the right or western bank of the river Vardar.

But meanwhile Greece and especially Serbia, which latter country had been compelled to withdraw from the Adriatic coast by Austria, and was further precluded from ever returning there by the creation of the independent state of Albania, determined to retain possession of all that part of Macedonia, including the whole valley of the Vardar with its important railway, which they had conquered, and thus secure their common frontier.

The great immemorial highway from the north-west to the Balkan peninsula crosses the Danube at Belgrade and follows the valley of the Morava to Nish; thence it branches off eastwards, going through Sofia and again crossing all Bulgaria to reach Constantinople, while the route to Salonika follows the Morava southwards from Nish and crosses the watershed into the valley of the Vardar, which flows into the Aegean.

But even this road, following the course of the rivers Morava and Vardar, only went through the fringe of Serb territory, and left untouched the vast mountain region between the Morava and the Adriatic, which is really the home of the Serb race.

After Stephen returned to Serbia he made an alliance with Hungary, which gave him back Belgrade and northern Serbia; it was at this time (1403) that Belgrade first became the capital, the political centre having in the course of fifty years moved from the Vardar to the Danube.

It had been agreed that Bulgaria, as its share of the spoils, should have all central Macedonia, with Monastir and Okhrida, although on ethnical grounds the Bulgarians have only very slightly better claim to the country and towns west of the Vardar than any of the other Balkan nationalities.

But at the time that the agreement had been concluded it had been calculated in Greece and Serbia that Albania, far from being made independent, would be divided between them, and that Serbia, assured of a strip of coast on the Adriatic, would have no interest in the control of the river Vardar and of the railway which follows its course connecting the interior of Serbia with the port of Salonika.

Bulgaria for its own part naturally refused to waive its claim to central Macedonia, well knowing that the master of the Vardar valley is master of the Balkan peninsula.

[Footnote 1: This was formed by the stream Zletovska, a tributary of the river Bregalnica, which in its turn falls into the Vardar on its left or eastern bank about 40 miles south of Skoplje (Üsküb).

At one o'clock in the morning of June 30 the Bulgarians, without provocation, without declaration of war, and without warning, crossed the Bregalnica (a tributary of the Vardar) and attacked the Serbs.

Some districts of east-central Macedonia, which were genuinely Bulgarian, were included in Serbian territory, as Serbia naturally did not wish, after the disquieting and costly experience of June and July 1913, to give the Bulgarians another chance of separating Greek from Serbian territory by a fresh surprise attack, and the further the Bulgarians could be kept from the Vardar river and railway the less likelihood there was of this.

In this concentration-area it gathered momentum during the earlier part of the seventh century A.D., and then burst out with irresistible force in all directions, eastward across the Maritsa basin till it reached the Black Sea, and southward down the Vardar to the shores of the Aegean.

A few fortified cities held out, Adrianople on the Maritsa continued to cover Constantinople; Salonika at the mouth of the Vardar survived a two hundred years siege; while further south Athens, Korinth, and Patras escaped extinction.