However, as the historian David Reynolds observed, "For most of the period since 1919, Anglo-American relations had been cool and often suspicious. United States 'betrayal' of the League of Nations was only the first in a series of US actions—over war debts, naval rivalry, the 1931–2 Manchurian crisis and the Depression—that convinced British leaders that the United States could not be relied on". Equally, as US President Harry S. Truman's Secretary of State, Dean Acheson, recalled, "Of course a unique relation existed between Britain and America—our common language and history ensured that. But unique did not mean affectionate. We had fought England as an enemy as often as we had fought by her side as an ally".