Plowing the Wikipedia, We Have found at Least 19 Nations concurrently at War Including Russia, Colombia and Acholiland

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Acholiland insurgency Israeli-Palestinian conflict Colombian armed conflict Insurgency in Jammu and Kashmir Iraq War Insurgency in the Philippines Fatah-Hamas conflict War in Somalia Turkey-PKK conflict Second Chechen War Insurgency in Ogaden South Thailand insurgency Sri Lankan Civil War War in Afghanistan War in North-West Pakistan War in Darfur Civil war in Chad Sa'dah insurgency South Ossetia War