וַיִּפְנ֖וּ וַיֵּלֵ֑כוּ וַיָּשִׂ֨ימוּ אֶת־הַטַּ֧ף וְאֶת־הַמִּקְנֶ֛ה וְאֶת־הַכְּבוּדָּ֖ה לִפְנֵיהֶֽם׃
So they turned and departed, and put the little ones and the cattle and the goods before them.
Rashi on Judges
The bulky cargo. The loads. Anything which moved ponderously, thus making it impossible to move quickly should the local inhabitants pursue them.