What resources or assets do you have, and are they sufficient for what you need?  Asking the question can identify resource gaps that may affect what you can realistically achieve.  It also, of course, identifies the support you do not have, but will need in order to proceed.

You should also map out any things that you are uncertain about or that might go wrong, and assess the possible impact of these risks on your project.  This puts you in a better position to determine how to manage these risks.  And while risk assessment will be a continuous thread throughout, it is imperative to identify the most obvious, or potentially most damaging threats, at this early stage.