Is it morally alright to sacrifice thousands of lives on the assumption that your enemy may cause a greater loss of life at some undetermined time in the future?

He said that "I believe it must be the policy of the United States to support free peoples who are resisting attempted subjugation [domination] by armed minorities or by outside pressure. Should we fail to aid Greece and Turkey in this fateful hour, the effect will be far-reaching to the West. The seeds of totalitarian regimes are nurtured by misery and want. They spread and grow in the evil soil of poverty and strife. They reach their full growth when the hope of a people for a better life has died. Therefore, I propose giving Greece and Turkey $400 million in aid."

Hope this helps.