to design, to invent / to devise, to develop, to think up (a plan, method, etc.)

regress, regression, retreat, recession

to regress, to retreat

war / battle, military hostilities

engage in war / engage in battle

a course in engineering / the study of engineering

public welfare, public benefit, public interest

a mascot

(mathematics) point or line of intersection / (astronomy) orbinal node

minister of a legation