The Abrams tanks that the United States intends to transfer to Ukraine are the modern M1A2, not the A1, which the US military has in stock, but they will also be stripped of their so-called secret armour, which includes depleted uranium.
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News Ukrainska Pravda
Why has Germany sent only 18 Leopard tanks? USA sending 31 Abrams tanks to Ukraine because there are 31 in a Ukraine tank battalion. Why don't others send in batches of 31? - Quora
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The Tank is Dead: Long Live the Tank