Andrew, you are on the right track.
The two fronts were with France and Russia. German assistance to Austria was going to mean war with Russia. France was allied with Russia, and it wanted revenge against Germany for its defeat in the Franco-Prussian War of 1870.
Germany knew that France would enter any conflict between Germany and Russia. This certainty is what led the German generals to plan for a quick invasion of France at the war’s beginning. The idea was that the war would not _really_ be on two fronts because it would take Russia months to mobilize. By the time Russia was ready to fight, German leaders wanted to have dealt with France already. They were sure they’d have to one way or the other. They were convinced that a “wait and see” approach would mean fighting both France and Russia simultaneously when both enemies were at maximum readiness.