Breakdown of Det var försvararen som tacklade anfallaren.
vara
to be
det
it (neuter)
som
who / which / that (relative pronoun)
anfallaren
the striker
Questions & Answers about Det var försvararen som tacklade anfallaren.
Why do we use det var... som here instead of just saying Försvararen tacklade anfallaren?
This structure is called a cleft sentence (utbrytning). We use it to emphasize a specific part of the sentence. By putting försvararen between det var (it was) and som (who/that), you are highlighting exactly who did the tackling, likely to correct someone who thought a different player did it.
The English translation uses 'who'. Why do we use som instead of vem?
In Swedish, vem is strictly a question word used to ask 'who?' (as in Vem tacklade honom?). When connecting sentences or clauses with 'who', 'which', or 'that', you must use the relative pronoun som. In cleft sentences, the connecting word is always som.
Why do both försvararen and anfallaren end in -aren?
Both of these nouns are formed from verbs (att försvara means to defend, and att anfalla means to attack). Adding the ending -are creates a noun for the person doing the action, similar to '-er' in English. To make these words definite ('the defender'), you add -n, resulting in the -aren ending.
How would the sentence change if we wanted to emphasize the striker instead ('It was the striker the defender tackled')?