Can a grenade shoot down a relatively thick tree?

I have been selected as an officer cadet and shall be heading into training within a few months. However, i am also due to have a novel published which i recently wrote. A friend tild me that as a military serviceman, i shall nkt be anbe to accept any royalties or payments after i get comissioned. Is that true? I cannot find a good answer through google.

I want to serve even if the novel becomes a...