how do I get textures to appear in the viewport?

I’m probably missing something basic, but days of searching have not revealed an answer.

I have the viewport shading mode set to textured. I created a mesh plane, and assigned it a material with an image texture. The texture shows up correctly when I render, but nothing I’ve tried makes it show up in the viewport’s real-time preview.

I have the object’s drawtype set to Shaded.

What am I missing?

only UV mapped textures are visible in the viewport (within reason (see post below)).

A texture must be UV mapped to show up in the 3D window.

Although I believe I’ve read that to show up otherwise, a mesh must be subdivided to a very high level . . . and yet the texture will still not be a very high resolution.