Significance The T6SS is a microscopic harpoon that bacteria use to deliver toxins into neighboring cells. While its complex assembly process has been extensively studied, it remains unclear how the two forms (long and short) of the pivotal TssA protein affect T6SS function. TssA promotes baseplate formation, orchestrates sheath extension and, in its long form, interacts with a partner protein to anchor the extending sheath at the opposing side of the cell for up to 10 min. Here we demonstrate that short TssA proteins assist sheath stabilization by associating with a yet undescribed class of T6SS proteins that accumulate at the baseplate. These T6SSs fire in seconds; therefore, this discovery provides insight into the mechanism underpinning the different fighting strategies observed across T6SS-carrying bacteria.