Mars in the 12th house (Vyaya, the house of loss & liberation) brings the significations of Mars, namely energy & courage, younger siblings, land & property, into the area of expenditure, foreign lands, isolation and spiritual liberation. The 12th house governs expenditure & loss, moksha & liberation, foreign lands, isolation & retreat.
Results of Mars in the 12th House
Mars is a malefic planet, so here it tends to bring anger, impulsiveness, accidents, conflict and disputes over property focused on expenditure, foreign lands, isolation and spiritual liberation. As the 12th is a dusthana (difficult) house, results may come through struggle before growth.The exact result depends on which sign Mars occupies here and the aspects it receives.
When It Activates
These results typically surface during the Vimshottari mahadasha or antardasha of Mars, and when transiting planets trigger the 12th house. A well-placed Mars here supports spiritual growth, gains from abroad and healthy detachment; when afflicted it can indicate heavy expenses, losses, isolation and hidden enemies.