He graduated from the Mikhailovsky Artillery School, served briefly as a line officer, then entered the General Staff Academy. He graduated with honors in 1892, and he went on to a distinguished career as a staff officer.
Danilov s first posting was to Kiev, where he specialized in mobilization problems. He soon found himself called to the General Staff in St. Petersburg; in addition to his regular duties, he taught at the General Staff Academy and helped edit the leading professional journals of the Russian army. In 1906 the rising young Genshtabist put the finishing touches to his preparation for higher responsibility by taking a turn in command of a field unit, the 166th Infantry Regiment. In 1908, as a colonel, he returned to the General Staff for a meteoric rise.
In the years up to 1914 Danilov served first as the chief of the General Staff's operations section and then rose to become the army's quartermaster general, that is, deputy chief of staff. Chiefs of staff came and went with bewildering speed, six in five years. It was Danilov, by 1909 promoted general, who provided an element of continuity to Russia's pre-World War I planning. With the controversial but reform-minded war minister, General Sukhomlinov, Danilov developed the so-called Plan 19. This plan advocated directing Russia's initial offensive in a future conflict with the Central Powers against Germany. Such an action would strike at the more potent member of the enemy alliance and was likely to help disrupt a German offensive against France, Russia's ally. A parallel suggestion called for abandoning Russia's antiquated collection of Polish fortresses. Danilov s plans encountered massive resistance; local commanders in the southwestern provinces who expected to face an Austrian onslaught at the start of a future war howled the loudest. In the end, Danilov saw his plan reshaped. Russia would begin the war with two offensives, one against the Germans in East Prussia; the other, and stronger, against Austrian Galicia. The stage was set for a serious dispersal of Russian strength.
During the July crisis of 1914, Danilov, by his own account, played a key role. He returned from an inspection tour of the Caucasus on July 26 to throw his weight in favor of general, not partial, mobilization. Thus, his may have been the decisive voice in bringing Russia to the ultimate confrontation with Germany. As the crisis showed, a strong hand at the top of Russia's military was mandatory. Instead, confusion prevailed. Tsar Nicholas II decided at the last moment not to take the supreme command, which went to his uncle, Grand Duke Nikolai Nikolaevich. The army's youthful new chief of staff, General Yanushkevich, was almost equally unfamiliar with Russia's war plans. Thus, it fell to Danilov to coordinate the widely divergent offensives against Germany and Austria-Hungary. His contemporaries credited Danilov with intelligence and a huge capacity for hard work, but events quickly spun out of control.
The southwestern front (or army group) against Austria-Hungary and the northwestern front (army group) against East Prussia went their independent ways. After Plan 19 had been revised, the north-western front under General Zhilinsky had been weakened to permit Russia to strike Austria and Germany simultaneously. Zhilinsky's remaining two armies, widely separated, could not support each other. In the last week of August, General Rennenkampf's First Army was bloodied; General Samsonovs Second Army was massacred. Meanwhile, in Galicia, a ponderous Russian advance westward along the Carpathians was too slow to cut off the Austrian armies that Conrad von Hotzendorf had boldly dispatched northward toward central Poland.
In mid-November, the slackness in the Russian command system was demonstrated anew. A German offensive southeastward from Thom caught the exposed Russian Second Army off guard as it advanced toward Silesia. A major encounter developed at Lodz, but no one could push Rennenkampf and his First Army forward rapidly enough to cut off portions of the attacking German forces that had become dangerously exposed. By the start of the new year, Danilov, backed by the offensive-minded grand duke, was ready to attack again. A new thrust at East Prussia in February barely got off the planning board before the Germans disrupted Russian hopes by striking first at Augustovo. The Russian High Command now turned elsewhere.
During the remainder of his term as director of Russian military operations, Danilov found his attention centered in southern Poland. After the failure in February, the main Russian effort shifted to the Carpathians. By April initial advances there set a dangerous fuse burning. German reinforcements rushed in under the capable General von Mackensen; and the Central Powers crashed through the Russians' thin defensive line at Gorlice in early May. The vast dimensions of the Polish salient had stretched Russian manpower and especially materiel to the limit. Effective coordination of the two great Russian fighting fronts was the only remedy, but this Danilov and Grand Duke Nikolai never achieved. As Mackensen cut northward, a strategic retreat as far as the San River promised to salvage something. Danilov refused. By June simultaneous enemy advances in Galicia and northern Poland set the stage for a grim retreat.
Not until August could the Russian forces halt. By then, all three of the top army leaders found their reputations in shreds. Grand Duke Nikolai Nikolaevich and General Yanushkevich were dispatched to the safety of the Caucasus. Danilov was ousted, but given a corps command in the main theater of operations. The British observer General Knox noted the great sense of relief that ran through the army at Danilov's demotion.
Danilov worked his way a rung or two back up the military ladder. By early 1917 he had become chief of staff of the northern front, and for a time thereafter he held command of the Fifth Army. He left his military career behind in the fall of 1917. The following year he emigrated to France, where he wrote his memoirs and a biography of Grand Duke Nikolai Nikolaevich, the commander for whom he had never been able to produce successes. Danilov died in exile in Paris on November 3, 1937.