If credibility were such a fragile commodity, we wouldn't have needed the Reagan buildup after the Russians blinked during the Cuban Missile Crisis, or in 1973 when they made noises about helping the Arabs in the Yom Kippur war and then backed down.
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In 1973, the Russians made noises about helping Arabs in the Yom Kippur war.
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Arabs were not involved at all in the Yom Kippur war.