What's actually happening
Mars takes roughly two years to complete one circuit of the zodiac, spending an average of six to seven weeks in each sign during direct motion. Aquarius is a fixed air sign, traditionally ruled by Saturn with Uranus as a modern co-ruler.
What the tradition makes of it
Mars in Aquarius is the drive organized around ideas and collective purpose. The motivation is less personal ambition and more principle: the sense that the system is wrong, that the current arrangement is insufficient, that something ought to be different — and the willingness to act on that conviction even when acting alone is required.
The tradition notes this placement's revolutionary tendency — not necessarily in the political sense, but in the sense of a genuine interest in changing what has been taken for granted. The action here is more often ideological than tactical.
The shadow is the detachment that can accompany the abstract motivation. Acting for "everyone" can sometimes mean acting for an abstraction that no specific person actually is — and the people in front of you get fewer resources than the cause you are fighting for.
How to actually use it
Act from principle. This is good weather for the collective effort, the system-change initiative, the stand taken on behalf of something larger than personal interest. Let the conviction about what is right be the source of the energy.
The practice is to check that the principle is serving actual people, not only the idea of them.
When in doubt
Who specifically benefits from what you are fighting for?