Sun Square Mars love Synastry ~ Excessive Ego
The Sun is the source of all energies. These energies stimulate the activities of the houses occupied by the transiting Sun and reinforce or weaken the planetary effects, depending on the Sun's aspect to the natal planet. When the Sun transits an inner planet, it may trigger a dormant aspect between that inner planet and a slower moving outer planet. If a planet is being transited by another planet when it is being transited by the Sun, the effect of the transit is strengthened.
Sun Square Mars
A Sun square Mars aspect emphasizes the challenge of assertiveness. Each partner brings enough ego into this relationship to cause an unhealthy amount of competition between you over who directs what. You can meet this challenge favorably if you can agree to place this energy toward a common goal. When the Sun person is square the Mars person you can feel challenged by your partners need for dominance.