ar airplanes were used mainly
for observation purposes: to find the location of enemy forts, trenches,
troops, and batteries; and to direct the fire of the aviator's own
batteries. Hundreds of photographs were taken by the airmen, rapidly
developed, and within thirty minutes the staff officers could be seen
studying them with microscopes to determine what changes had taken place
within the enemy's lines. Anchored balloons, too, were used for similar
purposes.

Airplane construction and use developed more rapidly than any other
feature in the war. After the observation machines, came the
battle-planes, whose first purpose was to clear the way and protect the
observation planes. Later, heavy machines for bombing expeditions were
constructed; and squadrons of airplanes now took part in every battle,
preceding the attacking party, and firing with machine-guns and bombs
upon the enemy's trenches or his massed troops back of the line.

[Illustration: Map]

THE RUSSIANS INVADE TURKEY IN ASIA.--In the early months of 1916
Russian troops met with success in an offensive in the part of Turkey
south of the Caucasus. This territory, known as Arme'nia, is inhabited
by a Christian population who for many years had been the victims of
Turkish persecutions; half a million were cruelly exterminated after
Turkey allied herself with Germany in 1914. The Russians advanced
steadily, inflicting serious defeats upon the Turkish forces. In
February they took possession of Erz'erum, a strongly fortified city of
Armenia. The capture of this point was of importance because it was a
step in the plan for cooeperation with the British armies which were
pushing their way north from the region of the Persian Gulf. It had the
further important result of interrupting Turkish plans for an invasion
of Egypt by way of the Isthmus of Suez, as Turkey was compelled to
concentrate her power for the defense of her own territory.

In April, Treb'izond, the most important city on the Turkish shore of
the Black Sea, surrendered to the invading Russian army. The Russians,
supported by fleets along the coast, had made the defense of the city
impossible. The fall of Trebizond was a very serious blow to the power
of Turkey in Asia Minor.

THE CAMPAIGN IN MESOPOTAMIA.--Part of the Allied plan in the east was
for the junction of Russian armies operating from the region of the
Caucasus with British troops from the land around the Persian Gulf.
While the Russians, a