Russia and Ukraine are building up huge armies, but they both have the same problem with using them in battle

Tech Insider
Russia Putin Shoigu Gerasimov military headquarters
President Vladimir Putin, Defense Minister Sergei Shoigu, left, and Army chief of staff Gen. Valery Gerasimov at a military headquarters in Rostov-on-Don on November 9.

GAVRIIL GRIGOROV/POOL/AFP via Getty Images

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