What was the nature of the Treaty of Rapallo signed in 1922 between Germany and the USSR?

The Treaty of Rapallo, signed in 1922, was significant in establishing a cooperative relationship between Germany and the USSR, particularly in the wake of World War I and the Treaty of Versailles. The correct answer recognizes that the treaty involved both economic agreements and clandestine military collaborations.

Following the punitive measures imposed on Germany by the Treaty of Versailles, which limited its military capabilities and economic interactions, the Rapallo Treaty allowed for a renewal of military cooperation that was kept secret from the Allied powers. This included provisions for the Germans to secretly train their military in the USSR, which was essential for Germany to circumvent the restrictions imposed on them.

Simultaneously, the treaty included important economic aspects that facilitated trade and investments between the two countries. This bilateral agreement allowed both nations to benefit from each other's resources amidst the isolation they faced from the West.

The other choices do not fully encapsulate the multifaceted nature of the treaty. While there may have been discussions regarding military alliances or trade, the comprehensive nature incorporating both elements is what fundamentally shaped the relationship established in Rapallo.