From what I understood regarding tradition, he always got someone else to do his dirty work for him.
If by dirty work you mean his assassinations of the innocent, that is not really 'battle'.
In my Islamic Education classes, Sirah section, we studied there are 2 types of battles 'Ghazwah' and 'Sariyyah'
The former being the type ofs battle where the prophet participated in himself. The latter where he just called for it and sent another person of his companion to take the lead.
"In every time and culture there are pressures to conform to the prevailing prejudices. But there are also, in every place and epoch, those who value the truth; who record the evidence faithfully. Future generations are in their debt." -Carl Sagan