After many months of hesitation, Rumania finally decided to enter the war on the side of the Allies and declared war on Austria, August 27. The next day Germany declared war on Rumania, and the issue was squarely joined in the Balkans, which then became the scene of a mighty struggle for the possession of Germany's road to Constantinople and the East. Tremendous activity at once began on the Balkan front, with Rumania's endeavor to aid Russia in cutting off Bulgaria and Turkey from the Central Powers. In the event of the success of this move, it was expected that the Allies would start a gigantic drive toward Constantinople.
The most important gain for either side in the Balkans up to the middle of September was the capture by the Bulgarians and Germans, on September 7, of the great fortress of Turtukai, fifty miles to the southeast of Bucharest, the Rumanian capital, and chief defense of the capital on that side. Russian troops were rushed to the aid of the Rumanians, and the loss of Turtukai was offset by Rumanian successes across the Hungarian border, where they captured a number of towns, driving the Austrian defenders before them as their invasion of Hungary progressed.
RUSSIAN ARMIES ACTIVE
By September 10, Russian troops were massed in great force in southeastern Rumania, and engaged the Bulgarians on the whole seventy-mile front from the Danube to the Black Sea, fighting fiercely to wrest the offensive from the enemy invading Rumania. In Transylvania the Rumanians were advancing rapidly, having captured the important town of Orsova, on the Danube, which gave them a grip on the Austrian second line of defense behind the mountains dividing Transylvania from Hungary. The entrance of Rumania into the war had increased the Austro-Hungarian front by about 380 miles, which military men regarded as altogether too long for the Teutonic armies to hold with any hope of success.
The Russians were also on September 10 winning ground in their campaign against Lemberg, the capital of Galicia. They had advanced until they were within artillery range of Halicz, an important railway junction sixty miles south of Lemberg. They had cut the railway line between Lemberg and Halicz, and the latter town was in flames.
ALLIED PROGRESS ON THE WESTERN FRONT
British and French successes on the Western front continued during the month of September, and the gains were encouraging to the Allies. On September 15 the British took Flers, Martinpuich, the important position known as the High Wood, Courcelette, and almost all of the Bouleaux Wood, and also stormed the German positions from Combles north to the Pozieres-Bapaume road, arriving within four miles of Bapaume and capturing 2,300 prisoners. A prominent feature of the attack was the use by the British of armored automobile trucks of unusual size and power, so constructed that they were able to cross trenches and shell-holes. These "tanks," as they were called, proved a genuine surprise to the enemy. They were said to be developed from American tractors of the "caterpillar" variety, which lay their own tracks as they proceed.
A two-mile trench system, believed to be impregnable, was stormed by the Allied forces near Thiepval September 17, while south of the Somme the French took the German trenches along a front of three miles. Next day more ground was taken in the advance toward Bapaume and German prisoners continued to fall into the Allies' hands. The number of Teuton captives taken during the Somme fighting from July 1 to September 22 was placed at 55,800 men and officers.
The month of September was remarkable for the great number of aerial combats on the western front and the efficiency developed in this mode of fighting. Many airplanes were shot down on both sides, but the Allies seemed to be gaining the mastery of the air. On a single day, September 24, over a hundred air combats were reported, during which fifty-seven airplanes were destroyed. On the same day two French airmen, in flights of 500 miles, dropped bombs on the Krupp works at Essen in Germany.
In a forward sweep near the end of the month the British took a number of German positions northeast of Combles, while the French advanced south of that point, so that the two armies almost surrounding it were scarcely a mile apart. A day later British and French troops entered Comibles from opposite sides and drove the Germans out. Continuing the drive from Thiepval, which had also been occupied, the British consolidated their positions and straightened their line a short distance from Bapaume, their objective point at this time. More than 5,000 German prisoners were taken September 26 and 27.