Rapallo and the secret German-Soviet training network

Once the early commercial schemes faltered, covert military collaboration became the more durable part of the relationship. The 1922 Treaty of Rapallo supplied a public diplomatic relationship behind which German and Soviet officers could live, train, and work together. Specialized bases supported chemical weapons, armoured-warfare doctrine, aviation, engineering, and the reverse engineering of foreign technology. By 1927, Lipetsk's German complement was roughly a thousand pilots, observers, engineers, and mechanics after the base began operating in 1924. That concentration of aviation personnel is the institutional bridge that makes a joint naval-aviation experiment conceivable.