  In this work we study the homotopy theory of coherent group actions from a
global point of view, where we allow both the group and the space acted upon to
vary. Using the model of Segal group actions and the model categorical
Grothendieck construction we construct a model category encompassing all Segal
group actions simultaneously. We then prove a global rectification result in
this setting. We proceed to develop a general truncation theory for the
model-categorical Grothendieck construction and apply it to the case of Segal
group actions. We give a simple characterization of $n$-truncated Segal group
actions and show that every Segal group action admits a convergent Postnikov
tower.
