Word for: Making stronger together

It seems there is no term to connote generally the idea of combining and making thereby a whole stronger than the uniting parts. The general verbs "coalesce", "amalgamate" and "unite" do not take into account anything else than the idea of combining. I would therefore use a phrase.

• to coalesce/amalgamate/unite into a whole stronger than are in isolation the contributing parts they constitute

SOED, 1995 ed., coalesce v. i. Grow or come together to form one whole; unite; combine; form a coalition.   LD MACAULAY    Who had bound himself..never to coalesce with Pitt.   C. DARWIN    The granules coalesce into larger masses.    M.GIROUARD    The elements that were to coalesce into 'Queen Anne'.

In a wide domain of application (organizations, groups of people, robots, etc.), there exist an adjective with the meaning of mutual reinforcement: symbiotic, SOED transf. and fig. mutually advantageous (from late 19th century). There is no corresponding verb.

ref. The mechanical characteristics and functionalities of individual robots in a collective symbiotic system are of the utmost importance in order to confer suitable capabilities to the symbiotic robot organisms.

A shorter phrase could now be "to coalesce symbiotically".

It has the defect that an explicit superiority of the whole over the parts is not clearly meant although it seems an ineluctable consequence.