estaban resguardando
-they/you were protecting
Imperfecto progresivo para el sujeto ellos/ellas/ustedes del verbo resguardar.

resguardar

Jorge Jiménez se percató que un contingente de la división élite de policía Cobras estaban resguardando el lugar donde los estudiantes se encontraban detenidos.
Jorge Jiménez saw that a contingent of the anti-riot elite police unit Cobras was guarding the place where students were detained and he addressed the Sub-Commisary to obtain access.
Palabra del día
encontrarse