Integration combines the logistical, social and technical systems of both organisations into a single one, which is more interfaces than either had before.
Why it matters when the plan changes
Integration combines the logistical, social and technical systems of two organisations into one, which is the moment interfaces multiply rather than shrink. For a period, both organisations are running their own decision routes, their own escalation paths and their own assumptions about who settles what, while a plan is being executed across the pair. Cross-unit commitments are already the least dependable part of execution in a single organisation, and research on strategy delivery finds only 9% of managers say they can rely on colleagues in other functions all the time. Integration multiplies these dependencies at the exact point when the informal habits that made the old ones work have gone.
The tension is speed against care. Integrating fast removes duplicate structures earlier, acting on incomplete information about which parts of the two organisations were load-bearing. Integrating slowly keeps that information but pays the coordination cost for longer. Both are defensible; only one is usually chosen deliberately.
In practice
Two sales organisations are merged and the new structure is announced on day thirty. Neither legacy pricing rule is formally retired, because each was held by a forum that no longer exists. For two quarters, deals are priced by whichever legacy route the account manager came from, and the margin number nobody can explain is the result.
Evidence
Integration combines the logistical, social and technical systems of the merging organisations into one new system, which is the point at which interfaces multiply.
Post-merger integration, Wikipedia (2026)Cross-unit commitments are the least dependable part of execution, and integration creates a large number of new ones at once.
Donald Sull, Rebecca Homkes and Charles Sull, Why Strategy Execution Unravels and What to Do About It, Harvard Business Review (2015)
What it cannot tell you
Post-merger integration describes the work of combining two organisations, not the quality of the strategic logic behind the deal. A well-run integration cannot rescue a deal that should not have happened, and the term is silent on whether the two organisations should have combined at all, only on how the combination is executed.
Questions
Because performance was measured inside each organisation, and integration creates commitments between them. A 2015 Harvard Business Review study by Donald Sull, Rebecca Homkes and Charles Sull found only 9% of managers can rely on colleagues in other functions all the time, and integration multiplies exactly these cross-unit commitments at once.
Decision rights on anything the plan depends on. Systems and structures are visible and get attention; the question of who now settles a pricing call or a sequencing choice is invisible and settles itself informally if nobody assigns it, usually in two different ways in two places.
Neither reliably. As the Post-merger integration entry on Wikipedia (2026) describes, the process combines the logistical, social and technical systems of both organisations into one, so fast trades information for speed while slow trades speed for information. What matters is that the choice is made deliberately, not by default.
A rule or a decision that was held by a forum which no longer exists. Both organisations had one, neither was formally retired, and the work continues on whichever version the individual doing it grew up with. The symptom is a number nobody can explain.
Until the interfaces the plan depends on have named owners and agreed sequences, which is a condition rather than a duration. Programmes are usually declared complete when the structures are in place, which is an earlier and different milestone from the one that matters.