The Authority is seeking a supplier to provide sustainment, support, maintenance, and transition services for a portfolio of legacy Defence support applications and associated integration services that underpin logistics, inventory management, engineering, munitions, maritime, and supply chain operations across Defence. The requirement will support the continued operation of a complex and interconnected application estate whilst enabling the progressive transition, migration, disaggregation, and retirement of legacy systems as replacement capabilities are introduced. The scope is expected to include service management, application support and maintenance, incident and problem management, configuration and release management, technical assurance, cyber security support, middleware and integration services, data management, and associated technical specialist services. The supplier will be required to support application interoperability, data extraction and migration activities, interface management, knowledge transfer, and system decommissioning activities as part of an overall transition strategy. The requirement includes support for business-critical and operationally significant systems that provide logistics visibility, inventory management, engineering support, munitions management, and associated information services. The supplier will be expected to maintain service availability, performance, security, and resilience whilst supporting the implementation of replacement systems and the controlled reduction of the legacy estate over the contract term. The contract is anticipated to be a managed sustainment and transition arrangement with a reducing application footprint, supporting ongoing modernisation activities through data migration, systems integration, retirement planning, and service transition support