Sforno on Numbers 10:2/ספורנו על במדבר י׳:ב׳

1עשה לך שתי חצוצרות כסף, seeing that the immediate plan was for the people to journey to the Holy Land without delay, G’d gave the commandment for the trumpets to be used as “Royal trumpet blasts,” announcing the moving of the Tabernacle to a new location, or announcing the arrival of the Tabernacle at its next location. The trumpets would also be blown before battles, as we know from verse 9.

2והיו לך למקרא העדה, to assemble the people or their leaders in front of the Tabernacle. G’d wanted that the trumpets be used to render honour to the king.