Reviewing the answers below and getting a feel for the line of thinking therein I am compelled to say that a project manager must be neither aggressive nor assertive when it comes to resources and schedules. A project manager must be collaborative and realistic when it comes to teams and schedules. A project manager is not a “direct-line people manager” for the teams. A project manager has no real authority over the team members and does not “make up” a schedule.

Here is where the aggressiveness and assertiveness come into play.

A project manager must be aggressive in championing the cause of the project project team customer needs leadership directives and organizational processes and best practices both inward and outward (to the project teams).

A project manager must be assertive in times or chaos confusion and doubt to provide clear direction and leadership to the team.

A project manager is someone who has zero authority and 100 accountability over his/her team activities. Therefore the focus is on the softer skills – how to motivate teams how to collaborate with teams how to understand others’ perspectives how to ensure work-life balance to the team members how to communicate with them effectively how to listen how to make the team want to follow and how to get more commitments from the team (not because they “have” to commit more but because they “want” to commit more).