asediar
besiege
siege
besiege
+
-ar
verb suffix
Asediar means to besiege and can be thought of as siege0 + -ar1 (verb1).
verb
  1. besiege
    To besiege or surround a place, typically with armed forces.
    El ejército enemigo asedió la ciudad durante meses. // The enemy army besieged the city for months.