Britain offered Cyprus to Royalist Greece as an inducement to join the allies in October 1915, with an additional offer of the Thracian littoral. Neither offer would budge King Constantine from his benevolent neutrality in the great war.

The British Minister in Athens, Sir Francis Elliot, consulted the former Greek premier, Eleftherios Venizelos about Britain’s additional offer. The latter told the former that the Thracian decision should only be made public when a large allied force arrived in Thessaloniki. It was one possible way of coercing the Greek General staff to join the allied cause. However, the Greek side distrusted the British because they had previously favored the Bulgarian side for a time, a situation which changed when Bulgaria joined the Central powers.

On October 20, 1915, the Russian Foreign Minister, Sergey Sazanov instructed the Russian minister in Athens to join with his British and French colleagues in promising the Bulgarian littoral of the Aegean in order for Greece to join the allies.

However, Sazanov thought that the allies were making a mistake in continuing to raise their offers to Greece. Sazanov thought that all these territorial offers would lower allied prestige and create an impression that the allies would pay any price for Greek cooperation. Sazanov believed the allies should fix a date for a definite Greek answer. Otherwise all offers would lapse.

There was a small Anglo-French force in Thessaloniki ready to go Serbia’s assistance. However, the Royalists were unhappy with their presence on Greek soil. Since Bulgaria joined the Central Powers, the British officer, Colonel Napier suggested to the French that an allied landing take place at Kavalla. Such a landing offered three advantages: “(1) it was a convenient base to attack Bulgaria and stop her from sending grain to Greece by cutting the railway line; (2) it would divert Bulgarian troops from Macedonia; (3) If Greece contemplates surrounding our troops at Salonica and forcing us to leave, it will enable us to frustrate that plan.”

Napier’s whole idea was to take control of the railway line by cutting Bulgarian communications along this part of the Thracian littoral.

On October 22, an allied squadron bombarded the Bulgaria controlled-coast between Port Lagos and Dedeagatch (Alexandroupolis) without a reply from the enemy. At Dedeagatch “a shipping warehouse, piers, a railway bridge on the east end of town and much rolling stock was destroyed. Several large fires were started, one evidently at an old torpedo depot. The residential part of the town was not destroyed.”

In 1913, Venizelos had recognized the importance of Dedeagatch and stated that it was where “three lines from Salonika, Adrianople, and Constantinople converge, which shows the importance and commercial value of this port.”

During October 1915, Elliot learned of unconfirmed reports of Serbian successes that gave the allies an opportunity to “encourage” Greek participation in the war. Besides the offer of Cyprus, the allies added Thrace as a further inducement to Greece. The allies would not object to Greece gaining possession of the Thracian littoral so long as she was “told at the same time that all previous offers would lapse unless accepted and acted on immediately.”

Unfortunately, Constantine remained steadfast to his neutral policy.

Serbia was being attacked from all sides by German-Austrian and Bulgarian forces. Elliot believed that an essential condition of Greek action was a large allied presence to stop Germans advancing southwards. The French War Minister, Alexandre Millerand recognized the serious situation in Serbia and considered the best course of action was to send additional troops to Thessaloniki. The French government thought that Britain should stop making promises to Greece and “show our strength by sending troops and also possibly using threats, letting it be known that a naval force was assembling, say at Canea.”

The British faced a complicated Balkan situation in sending troops to fight in the Near and Middle East fronts because of limits on how many troops she could withdraw from the western front in France. General Maurice Sarrail, the French commander, requested the allies quickly increase their troops numbers in the Thessaloniki district. Eventually British troops were transferred from the failed Gallipoli expedition to the Thessaloniki  front in January 1916.

Meanwhile, Colonel Napier believed that if Venizelos returned to power, Britain would again be able to offer Cyprus and the Bulgarian littoral in return for Greek action. The Bulgarian coast was of immense importance to Greece in the event of any future war with Bulgaria. If Bulgaria possessed a base in the Aegean Sea, she could effectively interrupt a Greek mobilization. Napier thought the provision of 200,000 Russian troops through Rumania, and the march of Greek and allied troops through the Bulgarian littoral to Constantinople would result in the defeat of Ottoman Turkey. Stopping the supply of German weapons reaching the enemy through Bulgarian territory was another way of cutting Germany’s communication with the Balkans. Napier never doubted the ultimate defeat of Germany.

Constantine continued his neutrality policy until his dethronement by the allies in June 1917. Venizelos returned to power as premier by declaring war on the Central Powers in July 1917. Greek troops fought alongside their Anglo-French allies on the Macedonian front in helping to defeat Bulgaria and leading to its capitulation in September 1918. The future of western and eastern Thrace and granting Bulgaria an outlet to the Aegean would be decided at peace conferences during the period 1919-23.