Note the second a in stratagem.
Both words refer to plans of action. But stratagem denotes trickery. It is a scheme to deceive or outwit.
Confusing Words and Homonyms
Letter A - B - C - D - E - F - G - H - I - J - K - L - M - N - O - P - Q - R - S - T - U - V - W - X - Y - Z