Rand study from April 2019 on prolonged Ukraine war

 Summary from Moon of Alabama:

The reports final policy advice concludes:

A dramatic, overnight shift in U.S. policy is politically impossible—both domestically and with allies—and would be unwise in any case. But developing these instruments now and socializing them with Ukraine and with U.S. allies might help catalyze the eventual start of a process that could bring this war to a negotiated end in a time frame that would serve U.S. interests. The alternative is a long war that poses major challenges for the United States, Ukraine, and the rest of the world.