1. To begin or set out on a journey or trip. We'll need to launch forth around 8 AM if we want to reach New York before dusk. The battalion of soldiers launched forth, heading toward an uncertain fate.
2. To issue, propel, or project something forward with force. In this usage, a noun or pronoun can be used between "launch" and "forth." The candidate launched forth another series of attacks against his opponents. We launched our boat forth into the water, hoping to catch the wind and continue our momentum. The great god launched forth his mighty lightning bolts down upon the inhabitants of the planet.
3. To begin or initiate some plan, undertaking, or project. In this usage, a noun or pronoun can be used between "launch" and "forth." The government will be launching forth its controversial new plan next month. The group of rebels launched forth their uprising in Spring of that year.
launch forth (upon something)
to set out on something; to begin on something, such as a journey or a long lecture or sermon. (Upon is formal and less commonly used than on.) We launched forth on our trip before dawn. What time shall we launch forth tomorrow morning?