The Passive Voice with "ser"
When we want to emphasize the person or thing receiving an action rather than the one performing it, we use the passive voice. While you already know the "se" passive for general statements, this analytic passive is often used in history and art to state exactly who performed the action.
To form this passive voice in the past tense, use the preterite forms of ser (usually fue or fueron) followed by a past participle.
If you want to mention the person who performed the action (the agent), use the preposition por (by).
| That portrait was painted by the king. | Ese retrato fue pintado por el rey. |
Agreement with the Subject
In this structure, the past participle acts like an adjective. It must agree in gender and number with the subject of the sentence (the thing that was created, designed, or restored).
| The tower was designed by a famous architect. | La torre fue diseñada por un arquitecto famoso. |
| The cathedral was restored by the government. | La catedral fue restaurada por el gobierno. |
This rule applies even with irregular past participles, like hecho (made/done).
| That sculpture was made in that era. | Esa escultura fue hecha en esa época. |
Omitting the Agent
Just like in English, you don't always have to include who did the action. If the creator or restorer is unknown or unimportant to the story, you can leave off the por phrase entirely.
| The palace was restored last year. | El palacio fue restaurado el año pasado. |
| The exhibition was inaugurated at noon. | La exposición fue inaugurada al mediodía. |