; or (2) limits on the number of National Guard personnel that may be placed on active duty for operational support under section 115 of title 10, United States Code. (f) Reimbursement required (1) In general The Secretary of Defense shall reimburse States for the cost of the deployment of any units or personnel of the National Guard to perform operations and missions in full-time State Active Duty in support of a southern border mission. The Secretary of Defense may not seek reimbursement from the Secretary for any reimbursements paid to States for the costs of such deployments. (2) Limitation The total amount of reimbursements under this section may not exceed $35,000,000 in any fiscal year. 1119. Operation Phalanx (a) In general The Secretary of Defense, with the concurrence of the Secretary, shall provide assistance to U.S. Customs and Border Protection for purposes of increasing ongoing efforts to secure the southern border. (b) Types of assistance authorized The assistance provided under subsection (a) may include— (1) deployment of manned aircraft, unmanned aerial surveillance systems, and ground-based surveillance systems to support continuous surveillance of the southern border