In search of protection, Bulgaria quickly aligned itself with the Allied Nations, who were short of allies. Specifically, Bulgaria connected with the Austro-Hungarian Empire, which was seeking to extend its influence over the Balkan Peninsula.
The Austro-Hungarian Empire was deeply concerned about the unity the Balkan League had previously displayed, which led to Russia controlling the Balkan situation.
Seeing Bulgaria approach them for help, the Austro-Hungarian Empire naturally found no excuse to refuse.
After recognising the anti-Bulgarian alliance brewing among the Balkan nations, Bulgaria did not hesitate to sign a sovereignty defense treaty with the Austro-Hungarian Empire.
The treaty stipulated that the Austro-Hungarian Empire would provide loans to Bulgaria, helping it maintain military preparation and domestic order.
In case Bulgaria's territorial safety was seriously threatened, they agreed to send troops to protect Bulgaria's independence and territorial integrity.
This treaty emboldened Bulgaria to believe that, with the support of the Austro-Hungarian Empire and security guarantees for Bulgaria, it could live free from worry, even taking the initiative to attack other Balkan nations.
In fact, this is exactly what Bulgaria did.
On May 19, 1913, after obtaining approval from Germany and the Austro-Hungarian Empire, Bulgaria took the first step in launching an attack against Greece and Serbia.
350,000 Bulgarian troops were distributed among 100,000 fighting against Greece, 150,000 against Serbia, and 100,000 reserve forces, who initiated an overwhelming offensive.
To fulfill their alliance obligation and stake a claim in the war, on May 23, Romania declared war on Bulgaria. It was an excuse for the war was Bulgaria's alleged destruction of Romanian borders while mobilizing its troops.
Britain and France's statement was actually a means to probe Arthur's attitude.
After all, as one of the Four Great Powers of the Allies, Australasia could not possibly stand apart if conflict erupted between the Allied Nations and the Allies.
Unless Arthur wanted to switch sides midway like Italy, he had to firmly support Britain, France and the Allies in order to maintain his position as one of the Four Great Powers of the Allies and ensure post-war benefits distribution.
After receiving an inquiry telegram from the British and French governments, Arthur responded quickly, stating that Australasia was ready to fight at any time and would do its utmost to support Britain, France, Russia and the entire Allied collective.
The firm stance of the Four Great Powers of the Allies put considerable pressure on the Three Great Powers of the Allied Nations, especially the strongest country—The German Empire.
Although the Austro-Hungarian Empire looked set to attack Serbia, after much thought, Germany ultimately decided to halt the Austro-Hungarian Empire's actions.
In June 1913, William II's letter to Emperor Francis, sent from Berlin to Vienna, clarified William II's attitude: "Supporting Bulgaria is certainly not wrong, but it would be somewhat loss-making if it caused a war with the Allies. It's not that we're afraid of them. From what I see, preparations for a world-level war have not yet been completed.
We should postpone all military actions against the Allied Nations until our military preparations are complete."
Even the slightly arrogant and temperamental William II had to admit that he was under overwhelming pressure when facing the Four Great Powers of the Allies.
France and Russia are located to the east and west of Germany, which means that if they were to fight against the Allies, Germany would have to endure the pressure of a two-front war.
If the combined land forces of France and Russia were enough to contain Germany's army, then the combined fleet of Britain and France could easily overwhelm the German High Seas Fleet.
The inclusion of Australasia in the Allies did not significantly boost the overall strength of the Allies.