In the immediate aftermath of World War II, there occurred several armed incidents between Yugoslavia and the Western Allies. Following the war, Yugoslavia acquired the Italian territory of Istria as well as the cities of Zadar and Rijeka. Yugoslav leadership was looking to incorporate Trieste into the country as well, which was opposed by the Western Allies. This led to several armed incidents, notably attacks by Yugoslav fighter planes on US transport aircraft, causing bitter criticism from the west. From 1945 to 1948, at least four US aircraft were shot down.[better source needed] Stalin was opposed to these provocations, as he felt the USSR unready to face the West in open war so soon after the losses of World War II and at the time when US had operational nuclear weapons whereas USSR had yet to conduct its first test. In addition, Tito was openly supportive of the Communist side in the Greek Civil War, while Stalin kept his distance, having agreed with Churchill not to pursue Soviet interests there, although he did support the Greek communist struggle politically, as demonstrated in several assemblies of the UN Security Council. In 1948, motivated by the desire to create a strong independent economy, Tito modeled his economic development plan independently from Moscow, which resulted in a diplomatic escalation followed by a bitter exchange of letters in which Tito affirmed that