For example,
He planned to go to Rome to study Italian.
→ It was to go to Rome to study Italian that he planned.
For example,
He planned to go to Rome to study Italian.
→ It was to go to Rome to study Italian that he planned.
The to-infinitival to go to Rome may not be separated from the verb that licenses it planned and foregrounded in the it-cleft construction. This is possible with objects - noun phrases, but not with to-infinitival complements.
It was her death that I desired.
* It was to kill her that I desired.
to-infinitivals may be foregrounded if they are adjuncts of purpose:
It was to study Italian that he planned to go to Rome.