Animating Characters - Blender to Unity

To begin with I am fairly new to Unity.

I am working on animations in Blender using Inverse Kinematics, as that is much, much easier.

Now, my understanding of Unity is that it is largely based on forward kinematics, so things like expressions will be ignored, and Unity will more or less just take the keyframes and interpolate the data between them itself.

I'm wondering how well that would work if I made only a few key frames. For instance, an attack animation: if I had, say, three keys set to poses through the animation (raise sword, midway through swing, and end swing) for a ten or fifteen frame animation, instead of keying in every frame or every other frame, would Unity be able to smoothly interpolate the data between them to some extent, and then revert back to the idle pose via blending? Or would this result in a shutter-y motion requiring more frequent keys?