Before the Battle of Dardanelles could be fought, Bulgaria thought it had seen the situation.

It was able to give Bulgaria such confidence, in addition to the Allied army, which was already unable to defeat Dardanelles, as well as the performance of Italy's participation in the war.

In April 1915, Italy and the Entente were preparing to declare war on Austria-Hungary after signing the Treaty of London because Britain and France had promised to divide Fum and Dalmatia after the war. Interestingly, out of fear of Germany, Italy declared war only against Austria-Hungary and did not dare to declare war on Germany until August 28, 1916.

As for Italy, Britain and France mainly needed their relatively strong navy. At this time, Italy had 3 dreadnoughts (one Dante-class, two Count Cavour-class), and if you add 3 Austro-Hungarian Combined Forces class, the Allies would have 6 dreadnoughts in the Mediterranean.

The French fleet, which was tasked with defending the Mediterranean, had only two dreadnoughts and two outfitting at the start of the war. And in order to ensure superiority over the German High Seas Fleet, Britain did not dare to easily send dreadnoughts to reinforce the Mediterranean. However, because of the territorial contradictions between Italy and Austria-Hungary, Italy chose to wait and see at the beginning of the war. Britain and France, seeing the rift in the Central Powers, stepped up their efforts to co-opt Italy.

This led to Italy's declaration of war on Austria-Hungary on May 23, 1915. At sea, Italy blockaded the Austro-Hungarian navy mainly with France, and on land Italy prepared an attack on Austria-Hungary.

The Italian army launched an attack on Austria-Hungary in the area of Izonzo, but due to the difficult terrain of the area and the fact that Austria-Hungary had built strong positions there. The Italian army, commanded by General Cadorna, was also guilty of the long preparation time of artillery (the mountainous terrain Italy prepared for a week of shelling, which depleted one-sixth of the already small Italian ammunition reserves), the dispersion of the battle lines, etc.

Moreover, the Italo-Austrian commanders had a simple but very different strategy for this campaign. The strategy of the Italian commander, Luigi Cadorna, was to attack, and he believed that only by attacking could a decisive result be obtained. Therefore, within half a year, the Italian army launched four large-scale attacks on the Austrian army in a row. In the face of these attacks, the Austrian commander, General Beauroch, adopted an extremely simple strategy. His countermeasure was to defend. Therefore, he gave only one order: "All troops should build fortifications and set up obstacles in front of them, and hold them in place." ”

In this way, with well-fortified fortifications, he was able to force the Italian army to fight in the unfavorable terrain of rivers and mountains. This tactic made him famous in the army and did not cause him much trouble in the early stages of the campaign. However, due to the low military quality of the Italian soldiers and the mediocre command of the officers. It allowed Italy to take the weakest major belligerent in World War I, but now Italy is still trying to attack Austria-Hungary, but the results are impressive.

General Cadore still insisted on the offensive strategy, but he still ignored two other important and complementary strategic factors. Concentrate forces and maximize them in decisive locations. Rational distribution, retaining the minimum necessary military means in non-decisive locations.

In 1915, the Italian decision-makers decided to launch an offensive on a 60-mile-wide front in Izonzzo, which made it impossible to concentrate their forces anywhere and weakened their forces materially and spiritually. Their attacks, as if forever uncoordinated, and inappropriate shelling often fell behind the infantry. In addition, since the Austrians occupied a lot of high ground, the attack could not be said to be a surprise, because the Austrians could see all the preparations of the Italian army from the high ground. As a result, the Italian army suffered 250,000 casualties and prisoners in about six months. The four main attacks were carried out in different locations, but all suffered heavy casualties and made little progress.

Italy's greatest achievement was the seizure of Podgora, the gateway to Gorizia, but Italy spent too much time doing so. After the Austro-Hungarian battle of Golice, they began to send troops to defend the border with Italy. And now, after recapturing Austrian Poland and inflicting heavy losses on the Russian army, Austria-Hungary has turned its attention to the southern front, and Serbia, the culprit of this European war, is still alive and kicking.

Since the outbreak of the war, Austria-Hungary has invaded Serbia three times, all of which have been repulsed by Serbia. This small country with a population of 4.3 million was desperate to resist the Austro-Hungarian invasion, and Serbia mobilized 400,000 troops at the beginning of the war. However, after three battles against Austria-Hungary, Serbia has extended its mobilization to women, and many Serbian armies have separate female units.

Even so, Serbia now has only more than 200,000 troops, and 16% of the country's population has been mobilized into the army, and almost all young and middle-aged people have been incorporated into the army. Even with such a desperate effort, Serbia does not have much military strength left. However, because Austria-Hungary was repulsed by Serbia three times, Bulgaria behind it became extremely important, and at this time an extremely important news came, Serbia had abnormal weather, due to the typhoid epidemic, about 150,000 Serbian soldiers were infected and incapacitated.

Austria-Hungary stepped up its efforts to win over Bulgaria, and finally assured Bulgaria that the Serbian territories it had seized would be extended to the central Kruševac region. Faced with this temptation, and the impact of the loss of the important Russian town of Warsaw, Bulgaria finally decided to join the Allies in the war.

The preliminary political and military negotiations for Galia's entry into the war were completed on September 6, 1915. In Sofia, the capital of Bulgaria, and in Germany, respectively, the German command of the Eastern Front, the German command of Preles and the German-Austrian armies, signed 3 documents, 2 political and 1 military. On the same day, Ottoman Turkey and Bulgaria signed a treaty to adjust the borders of the two countries.

Militarily, it was mainly a plan for the final settlement of Serbia. To this end, on 22 September, Bulgaria issued a general mobilization order. By the day of the war, a total of 616,680 people had been mobilized, and the total population of Bulgaria at that time was 4.93 million, of which 2,484,122 were men.

Now Serbia was completely unaware of the malice from behind Bulgaria, they were still focused on the German-Austrian army in front, this attack on Serbia, Austria-Hungary finally pulled the German army over, and the German 11th Army (7 German divisions) joined the invasion of Serbia. So Serbia now has no energy at all to care about Bulgaria behind it, and now they are all defending their troops against the German-Austrian army.