...Taken together, the embittered relations between Soviet personnel and Spaniards in the Republican zone, Moscow's linguistic deficiencies, and the Republican government's minimal support of its embassy are all symptoms of a more general problem in the affairs between the Soviet Union and Loyalist Spain.
On a fundamental level, there existed a constant friction that no amount of rhetoric about the fraternity of the two peoples could overcome. Ultimately, the two states possessed too little mutual cultural understanding, diplomatic precedence, and linguistic expertise to bridge the geographic and historic gap between them.
The Soviets, despite having had a presence in Spain since the early 1930s, grasped very little about the Republic, while the Republican leadership seemed to have only limited curiosity about the Soviet Union... Many Spanish Republicans were suspicious of Moscow's presence from the start, and accepted Stalin's help only to stave off immediate annihilation.
In the Spanish theater, the Soviets possessed none of the requisite characteristics of a strong and imposing foreign power; the Kremlin's physical distance from Spain was so great as to render the problem of extended supply, surveillance, and control all but impossible.
The Soviet leadership could barely keep track of their own representatives on the ground, much less infiltrate and control the myriad institutions of Republican Spain.
In terms of their sheer numbers, the Soviet presence barely rose to the level of a token force. Just over two thousand Soviet personnel served over the course of the long war—hardly a domineering contribution in a struggle that saw the mobilization of over a million men under arms—and two-thirds of these were engaged as relatively low-level pilots, tankers, technicians, and other support staff.
In some key battles and on entire fronts, the Soviet presence was almost nil.