When threatened, Putin will push back
The United States should not send weapons to Ukraine. First, Ukraine does not have a reliable and professional military, and this means the United States will have no control over how the weapons are used on the ground. They could be used to target opposing civilians by hyper-nationalist militias; they could even be used against targets in Russia by those who want to provoke a wider war. Second, the plan is based on the assumption that more weapons will deter Putin from taking further action or cause him to back down. But everything we know about Putin’s personality says that when he is threatened he will fight harder. Furthermore, he cannot be seen as backing down in the face of a Western threat and still maintain the image he has carefully cultivated as a strongman. He has been preparing the ground for the possibility of open Russian military involvement in Ukraine by saying that the conflict is really NATO’s attempt to threaten Russian sovereignty and security. He is most likely to ramp up the conflict, not tamp it down, if the United States sends weapons to Ukraine.