# Why is Disturbance Force Equal to Total Force in Stokes Flow?

So this step confuses me. Why is it true that the disturbance force is the total force in stokes flow? Any advice or guidance would be great!

From Pozrikidis' book:

Steady Stokes flow is described by $$\nabla\cdot\mathbf{T}=0$$, where $$\mathbf{T}=-p\boldsymbol{\delta}+\boldsymbol{\sigma}$$ is the total stress tensor. $$\mathbf{T}$$ is the stress exerted on each other by adjoining fluid particles at their contact area. $$\nabla\cdot\mathbf{T}$$ is the net surface force acting on a fluid particle due to its surrounding fluid, which is zero for Stokes flow (by definition). Thus the base flow velocity field (that in the absence of particle) doesn't give rise to net force.