Control Image Height with HTML

I have inserted some images into a post as the medium size with a width of 300. I removed the width definition and am trying to adjust the height using html but no matter what I set the height to, it never changes anything. I also removed the “medium” in the img src line. Here’s the code I have now: <img src="http://url.com/wp-content/uploads/2015/05/image-221x300.jpg" height="100" align="left" />

I’ve tried referencing the different image file without the size part but it still doesn’t change anything: <img src="http://url.com/wp-content/uploads/2015/05/image.jpg" height="100" align="left" />

Is there anyway to just manually set the image height or width just using the html? Or am I doing something wrong?

I’m using the Montezuma theme.