Mars is how you act and how you fight. Not what you want, that is Venus and the rest of the chart. Mars is the engine: the initiative, the way you begin, the energy you have to keep at it, the form your anger takes and what you do when you need to defend what is yours.

And here is what almost no text explains, though it changes the whole reading: Mars is the first piece of the chart that does not depend on your Sun. Mercury can only fall in three signs and Venus in five, because both stay chained to the Sun. Mars can be in any of the twelve, including the sign opposite yours.

That is why this is precisely where most people do not recognise themselves in the description of their own Sun sign. Sun in Libra with Mars in Aries is the most diplomatic person in the room and the one who fights worst when they finally fight; Sun in Aries with Mars in Pisces decides everything on the spot and cannot collect a debt of a hundred reais. Neither of them is wrong about themselves, both are reading only half the chart.

Having Mars in Sagittarius means you start a great deal and that your anger passes fast. The engine is enthusiasm. This person throws themselves into a big project with a faith that convinces others to come along, and loses interest when the thing turns into administration.

Mars is the planet of action; in Sagittarius it turns broad, frank and optimistic. This person says what they think without calculating the effect, takes more risk than average and recovers from a fall at a speed that is impressive.

And here is what hardly any text writes down: they are not irresponsible: they overestimate what fits in a week, and they do it in good faith every time. The miscalculation is always to the same side. This Mars sees the destination clearly and the route optimistically, and so it promises a deadline that does not exist. Whoever works with someone like this learns to double whatever number they say.

There is a second piece that changes everything: which house that Mars fell in, the area of life where that energy works. Mars in Sagittarius in house 9 fights over ideas, travels and teaches; in house 2, it risks money with a confidence that sometimes works out. The sign says HOW; the house says WHERE.

It shows up in the size of what this person promises and in how long they think it takes. These are concrete signs, the kind you recognise in your own week:

• tells the truth at the wrong moment, and is right
• starts a big project and gets bored in the administrative part
• anger rises fast, comes out whole and vanishes leaving no resentment
• needs movement, travel, novelty in order not to seize up
• defends a principle with a conviction that runs the other person over
• bets more than average, and recovers from the fall faster too

Notice what that list does not say. It does not say the person is irresponsible or over the top, two labels this position carries that describe the excess, not the position. It says their energy is broad, optimistic and needs a horizon.

The strength is daring: this person tries what others do not even consider. They do not freeze at the size of the thing, take a risk with what they have and start again after failing without burying themselves in shame, and since most opportunities require exactly that, they live a life with more chapters than average.

In practice this turns into three useful things: a courage to bet that opens doors no planning would open; a contagious enthusiasm that moves people towards a project with no promise of money; and a frankness that saves months of misunderstanding.

That strength does best in a venture, teaching, travel, sport, a cause, big sales and any work with a horizon and no leash. And it does badly in an office routine, a post of meticulous execution, a rigidly hierarchical environment and anywhere telling the truth costs you the job.

There are two, and they are opposites: the excess is daring turning into recklessness, and the deficiency is someone who learned their own anger was unacceptable and switched the whole engine off. The Shelly Method reads every archetype through four faces, the light, the shadow, the excess and the deficiency, and it is the last of them that hardly any text mentions.

The excess is betting without doing the sums: taking on three projects that do not fit, promising a deadline that does not exist, risking money that is needed. It also shows up as frankness with no brake, saying the truth nobody asked for, in the wrong tone, and calling the wound it caused sincerity.

The deficiency is the opposite and it hurts more, and in Mars it is the commonest of the twelve series on this blog: anger is the emotion almost every child was taught to keep to themselves, and many women heard it with extra insistence. A Mars in Sagittarius told they were irresponsible, or a dreamer, stops taking risks. They start accepting the safe job, not saying what they think, laughing at their own enthusiasm before anyone else does, and become someone bitter, cynical about anyone who tries, with a restlessness they explain as realism. It is the costliest loss of this position, and it is learned.

Both faces have the same raw material, and that is why the repair is the same: a daring that needs the sums done, not less daring. It is not solved by asking the person to be realistic, realism by decree turns into discouragement. It is solved with one step: before taking it on, write down the deadline and double it, and that is what the house of Mars and the rest of the chart show.

It matures when the person learns to finish one thing before starting the next, and that is worth more than any attempt to learn to dream less. Daring goes on being the talent; what changes is that it starts arriving with the sums attached.

There is a rhythm that helps to understand the arc, and it belongs to Mars itself: roughly every two years, it comes back to the exact degree it was at when you were born. It is the Mars return, and it works like the restart of a cycle, the urge to begin something else tends to land there, and that is no coincidence. For those with Mars in Sagittarius, this return arrives as an urge to move everything somewhere else, and sometimes that is exactly it.

And roughly every twenty-six months it turns retrograde for about nine weeks. These are the weeks when action jams: what was moving gets stuck, anger rises with no target and starting over takes more work than usual. For this Mars, they jam precisely what it hates seeing still, and they are the most irritating weeks of the cycle.

Maturity here is not learning to be afraid. It is the person coming to tell the risk they calculated from the one they simply did not look at. A mature Mars in Sagittarius goes on betting, and starts knowing how much it can lose, and it is that sum that turns recklessness into courage.

No honest text gives an age for this. The arc depends on the whole chart and on the life the person had.

It says how you act, and not what you should do nor whether you will manage it, and that distinction is the worst-made one in popular astrology. Mars is the engine; the destination is your choice.

Which house that Mars fell in changes the area where that energy works: Mars in Sagittarius in house 5 lives many stories and tells them even better; in house 10 it builds a career in leaps and not in steps. See the series The Sun in the 12 houses to understand what each house means.

Your Sun sign does not limit this one, and that is what sets Mars apart from Mercury and Venus. What counts is the combination: see the series The Sun in the 12 signs and compare.

And there is Venus, which says what attracts you. Mars in Sagittarius with a Venus that asks for the opposite produces someone who wants one thing and does another, and it is that mismatch, and not the sign on its own, that usually explains the complaint. See the series Venus in the 12 signs, and also The Moon in the 12 signs, which says what you need on the inside.

One limit said out loud, because it is also part of reading seriously: none of this is a diagnosis. Astrology describes tendency and gives vocabulary for what a person already lives; it does not measure health, does not explain physical pain and does not replace a doctor, therapy or a decision of your own.

And the questions that come up most on this subject, with the short answer: