Before revision:  We expanded our model of spindle rocking and predicted then experimentally validated that the oscillation onset position resists changes in cellular geometry and number of force generators. Consistent with final spindle position measurements, this new model accounts for a lower dependence on force generator dynamics and quantities than predicted by the previous model. Conclusion: The spindleposition regulates the rapid increase in forces needed for anaphase oscillation and positioning through the spatial modulation of microtubule-cortex contacts .
After revision:  We modelled this control, predicting and experimentally validating that the posterior crescent extent controlled where the anaphase oscillations started, in addition to mitotic progression. Finally, we propose that spatially restricting force generator to a posterior crescent sets the spindle's final position, reflecting polarity through the LET-99 dependent restriction of force generators to a posterior crescent .