Although mech was expected to be the main composition of Terran for Heart of the Swarm, most players opted for the standard Marine Tank composition when the expansion was just released. The new Medivac speed boost ability was often cited as the reason for the choice. However, Medivac had been heavily used in mech recently.
The typical approach for a marine tank opening against a mech opening is to switch to pure bio build. This is seen as the only possible solution to mech. Thorzain provided an alternative approach to this problem.