It is logical to think that ו is the conjunction that means and, ל is the preposition that means to, for, and maybe ה is the article.
If we are right, dictionaries would offer תחיל. But it is not the case.
So, letter ה is not the article.
Maybe, then, we face here prefix הת־? If this is prefix we should think of a word PI-d, probably PI-d050. But this is not possible because of the presence of preposition ל. Preposition ל does never precede a Past verb form.
Instead, preposition ל often precedes an Infinitive.
If this is the case of our word, then התחיל would be an Infinitive. Now, is this possible?
The answer leans to the yes: look at ptr PI-t2-022. Verb תָּחַל means to begin. But it is used in the Hiph'il conjugation.
Then, and to begin.