Initial causes (como)

To explain the reason or cause for a situation before stating the outcome—like explaining why a deep-sea submarine dive had to be aborted—start your sentence with como.

When used this way, como translates to "as" or "since."

As we had a critical failure, we decided to abort.
Como tuvimos un fallo crítico, decidimos abortar.
Since the indicator was showing a danger, the crew canceled the trip.
Como el indicador mostraba un peligro, la tripulación canceló el viaje.

The verb following como stays in the normal indicative mood, whether you are talking about the present or the past.

Since the submarine is submerging very fast, the alarm is ringing.
Como el submarino se está sumergiendo muy rápido, suena la alarma.
Since they didn't look at the indicator, they didn't notice the critical failure.
Como no miraron el indicador, no notaron el fallo crítico.

While you typically use porque (because) when the reason is attached to the middle or end of a statement, como is your go-to word when the reason comes first.

As the weather was unstable, the captain decided to abort the mission.
Como el clima estaba inestable, el capitán decidió abortar la misión.